About Locked and Unlocked Dimensions
You can lock dimensions in Sketcher. Locking of dimensions allows you to avoid modifications made to the sections outside the Sketcher mode by accidentally dragging a vertex or an entity. The locked state of the dimension is maintained when you quit or re-enter Sketcher mode.
You can also set Sketcher to lock all user-defined dimensions automatically by setting the value of the sketcher_dimension_autolock configuration option to yes. Alternatively, click > 
Options > > .
Options > > .After you set this option, all dimensions that you subsequently create or modify are locked. Dimensions created before you set automatic locking maintain their status.
 | The locked state of a dimension is not retained if the dimension is referenced in a relation, as the relation takes priority over the locked status of the dimension. |
To unlock a selected dimension, right-click and choose Unlock on the mini toolbar.
You can set the color for locked dimensions by clicking > Options > > . Select a color in the Locked dimension area.
Options > > . Select a color in the Locked dimension area.