The Place Constraint command provides several different constraint types. The Mate constraint is selected by default when the command is activated and is suitable for all the constraints needed in this tutorial.
Any constraint type requires that you select geometry on two parts. In the next step, you place a mate constraint between the top face of the panel part and the inside back face of the box part.
The selected face highlights and the direction indicator shows the constraint vector.
By default, Place Constraint previews the constraint automatically. It is only a preview and the constraint is not yet complete.
The Place Constraint command remains active and ready for the next constraint set.