Associating Dimensions with Elements
An association point in a dimension element is one that is associated with a point in the dimensioned element(s). Association points are most useful for points that are "connected" to the element being dimensioned, such as dimension endpoints.
To place association points, Association Lock and Snap Lock must be on. (Turning Association Lock on automatically turns Snap Lock on.) Dimensions must be placed as dimension elements to have association points. Association Lock can be set in the tool setting controls for dimensioning tools as well as in the Settings menu's Locks submenu.