Constrain the collinearity between two linear objects. If one line is moved, the other constrained line adjusts to remain aligned. The lines do not need to be aligned when you place the constraint; the first line moves to become collinear to the second line.
To constrain the collinearity between two lines:
Click the Constrain Collinear tool from the Dims/Notes tool set.
Multiple dimensional constraint tools share the same position on the tool set. Click and hold the mouse on the visible tool to open the Pop-out Tools list and select the desired tool.
Click the line to constrain.
The cursor switches to the bull’s-eye cursor.
Click the line to be constrained.
Green collinear constraint indicators are drawn on the two lines.