Revit Constraints and Locking: How to Use Them Safely
A Revit constraint is a rule that keeps one element tied to another. A lock turns a one-off move into that rule. Lock an alignment or a dimension and Revit keeps the relationship when the model changes. That is powerful in a family or a grid layout, and it is the reason a wall sometimes refuses to move. This guide covers how to set constraints, how to see them, how to remove them, and when to leave them alone.
TL;DR
A constraint is a lasting relationship between elements. You create one by clicking a padlock on an alignment or a permanent dimension, or by using an equality (EQ) constraint.
Constraints show as blue dashed lines and exist independently of dimensions. Deleting a dimension does not always remove the restriction.
Lock sparingly in project files. Lock deliberately in families, and flex the geometry after each lock.
In a workshared model, you cannot edit a constraint if any constrained element sits in a workset you cannot edit.
Revit already maintains many relationships itself, such as joined walls. Do not add manual locks on top.
Table of Contents
What a Revit constraint actually does
Without a constraint, Revit lets you move things freely. With one, the element follows its partner. Autodesk describes constraints as the way to establish and maintain relationships between elements in the model, and the rule stays in force while the design changes.
Two kinds exist, and the difference explains most of the confusion readers have:
Explicit constraints are the ones you create: a locked alignment, a locked dimension, an EQ constraint.
Implied constraints are managed by Revit. Joining walls at a corner or attaching a wall to a roof are examples. Autodesk’s documentation on constraints covers this, and it is the first place to look when a relationship seems to exist but you never made it.
Beginners often add manual locks to relationships Revit already looks after. The result is extra complexity and, sometimes, conflicts. If two walls are joined and behaving, leave them.
The three ways to lock in Revit
1. Align with the padlock
The Align tool (shortcut AL) moves one element to another. Before you click the second element, a padlock appears in the options area. Click it and the alignment becomes a permanent constraint.
Example: you align the face of an exterior wall to a grid line and lock it. Move the grid and the wall follows. This is what you want for a facade that must stay on its structural grid, and exactly what you do not want if someone later needs to nudge the wall by 50 mm.
A tip that comes up often on the Autodesk forums: when a family element locks to a plane you did not intend, draw it off to the side first, then use Align to move it into place. That way you choose what it locks to, instead of Revit picking whatever was nearest when you drew it.
2. Lock a permanent dimension
Place a dimension, select it, and click the padlock that appears. According to Autodesk, you can lock a permanent dimension to create a constraint, and a locked dimension cannot be changed by typing a new value until you unlock it. The locking permanent dimensions page confirms that locking restricts the movement of the referenced elements, and that clicking the padlock again toggles it off.
If you are unsure which dimension is which, our guide to Revit dimension types explains the difference between permanent, temporary and listening dimensions.
3. Equality (EQ) constraints
Select a multi-segment dimension and click the EQ symbol. Revit keeps the segments equal. This is ideal for evenly spaced grids, mullions, or a row of columns between two fixed ends. Change the overall length and every segment adjusts together.
Seeing what is locked
A locked dimension or alignment is represented by a constraint element. These are not view-specific. They appear as blue dashed lines in every view where their references are visible, while ordinary dimensions belong to one view only. That explains a classic puzzle: you cannot see a dimension in a plan, yet the element still will not move, because the constraint is visible in another view or exists with no dimension at all.
A practical way to hunt for them:
Select the element that will not move.
Look for padlock icons and blue dashed lines near its edges.
If nothing shows, check a section or elevation, where the referenced elements may be visible.
In family editing, tangency locks only appear when you select the line or arc that carries them, so you will not see every lock at once.
How to remove or release a constraint
Removing constraints keeps a model from becoming over-constrained, and Autodesk lists the options: click a lock to unlock it, click the EQ symbol to remove an equality constraint, or delete the dimension.
Situation | What to do |
Locked dimension | Select it and click the padlock to unlock |
EQ constraint | Select the dimension and click the EQ symbol |
Dimension you want to delete | Delete it, then choose in the prompt whether to delete or keep the constraint |
Dimension already gone, element still stuck | Select the blue dashed constraint line and delete it |
Temporary release while dragging | Unlock first, move, then relock if the rule still applies |
The fourth row is the one that catches people. The constraint can outlive the dimension. When you delete a dimension that carries a constraint, Revit asks whether to delete the constraint or keep it. Choose carefully: keeping it leaves an invisible restriction behind.
A short worked example
Suppose a partition is locked 3,000 mm from a column grid and your lead asks you to move it 200 mm. You drag it and nothing happens, or Revit shows a warning. Do this:
Select the partition and look for the padlock or blue dashed line.
Click the padlock to unlock.
Move the partition to the new position.
Decide whether the new position needs a lock. If the design intent is now “3,200 mm from the grid”, place a new dimension and lock that.
The point is that the lock records design intent. When the intent changes, you change the lock, not fight it.
When constraints go wrong
Over-constrained and conflicting
If two locks demand incompatible things, Revit raises an error and the change will not go through. Explicit constraint conflicts must be resolved before the model can update. The fix is nearly always the same: remove the lock that no longer serves the design, rather than adding another to compensate.
AutoCAD works similarly. It prevents constraints that would over-constrain the geometry, and removes constraints that become invalid after an edit. In AutoCAD, the DELCONSTRAINT command clears constraints from selected objects, and tapping Shift while selecting a grip relaxes them temporarily. Autodesk’s suggested order there is also useful in Revit families: define shape first with geometric relationships, then define size with dimensions.
Worksets block editing
In a shared model, constraints are bound by worksets. If any element involved sits in a workset you cannot edit, you cannot add or change the constraint. When you see a “cannot edit” message while locking, check ownership before you assume the lock is broken. The same issue appears with linked files, so a stable linking setup helps; see our Revit links workflow guide. If shared models are your daily reality, our Worksharing course covers worksets and ownership in depth.
Nested families and model text
Some errors, such as constraints that cannot be satisfied when locking model text in a family, come from nested geometry. A common workaround from the Autodesk forum threads is to build the nested object as its own family, load it into the host family, constrain it there, and adjust the origin of the host if needed. If a lock fails in a nested family, simplify first.
Constraints in families: where locking matters most
Project files need very few locks. Families need many. Autodesk’s own family guidance says to use reference planes to define every critical position, static and variable, so the geometry follows when those planes move. Its guidance on constraining family geometry says the sketches of the geometry should be constrained to the parametric framework you built first.
A reliable sequence:
Draw reference planes and name the ones that drive parameters.
Dimension between the planes and assign parameters.
Flex: change each parameter value and confirm the planes move.
Only then add geometry and lock it to the planes.
Flex again. If something stays put or throws an error, you have a broken or over-constrained condition, and it is far easier to fix now than after ten more locks.
We go deeper on the framework in Datum First Revit Reference Planes, and you can practice the whole sequence in Build One Parametric Revit Family in One Sitting.
Our perspective on when to lock
We teach Revit to architects and technicians every day, and the same pattern repeats. People discover the padlock, lock everything for a week, and then cannot edit their own model. The old advice from long-time users on the Autodesk community forums still holds: new users should hold off on locking until they have a feel for how Revit’s parametric behavior works, otherwise the project gets complicated and slow.
Our rule of thumb is simple. In a project, lock only what represents a real design rule: facade to grid, stair to level, a fixed clear width between two walls. In a family, lock almost everything to reference planes, and flex after each step. If you cannot explain in one sentence why something is locked, it should probably not be.
The other habit we push is reading what already exists before adding to it. Check for joins, attachments and existing blue dashed lines first. If you want a broader look at the habits that cause these problems, our article on common Revit modeling mistakes is a good companion. Reading drawings properly matters too, and this guide to reading construction drawings shows how to interpret what a set is telling you before you model it.
— Steve
A habit checklist for cleaner models
Name your intent. Before you lock, say what the lock represents.
Lock to datums, not to geometry. Grids, levels and reference planes move predictably. Random wall faces do not.
Flex early. Test parameter changes immediately after each lock.
Do not duplicate Revit’s own logic. Joined walls and attached tops need no extra lock.
Release before moving. Unlock, move, then decide whether to relock.
Check worksets. If a lock will not take, confirm you can edit every workset involved.
Clean up on handover. Search for stale constraints before you issue a model to another team.
Matching views matter here as well. Constraint elements are visible in all views where their references appear, but dimensions are view-specific, so check more than one view. Our guides to view range and section boxes in 3D views help when what you need is hidden by view settings rather than by a lock.
Learn it on a real project
Constraints make sense once you see them break and fix them yourself. Our Revit Course Only is €79 one-off and takes you from beginner to advanced through project-based lessons, with trainer support, lifetime access to the materials and a completion certificate. If you are brand new, the Revit Introduction at €20 is a lighter start. The course comes with a money-back guarantee.
FAQ
How do I lock things in Revit?
Use the Align tool (AL), pick the reference and then the element, and click the padlock before moving on. For dimensions, select a permanent dimension and click its padlock. Either method creates a constraint that stays in force until you unlock it.
How do I set constraints in Revit?
The three main routes are a locked alignment, a locked permanent dimension and an EQ constraint on a multi-segment dimension. In families, start by drawing reference planes, add parameters, and constrain geometry to the planes. Flex the family after each step to confirm it behaves.
How do I get rid of constraints in Revit?
Click the padlock to unlock, or click the EQ symbol to remove equality. If you delete a dimension, Revit asks whether to keep or delete its constraint. If an element is still stuck, select the blue dashed constraint line and delete it.
Why can’t I lock or edit a constraint in a shared model?
Constraints depend on worksets. If any element in the constraint is in a workset you cannot edit, you cannot add or change it. Request editing rights from the owner or ask them to relinquish, then try again.
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