The sides of each profile increases the surface area for gluing, resulting in a strong bond, stronger than a butt joint but not very visually appealing.
Finger joints are generally created by using identical profiles for both pieces.
They are made complementary by rotation or translation of the tool with respect to the workpiece.
Manual cutting of finger joints is time-consuming and error prone hence rarely done except in craft pieces.
The finger joint can also be valuable when creating baseboards, moulding or trim, and can be used in such things as floor boards, and door construction.