The biscuit joiner has been a part of my tool arsenal for over twenty years. The K-20 biscuit is made of plastic and has teeth or barbs molded into it. It is actually a bit wider than the standard wood biscuit and so it needs to be tapped into the slot with a mallet. This gives them tremendous holding power. On a recent project, I built a 16' x 8' cherry book case that was installed wall to wall and scribed in all around (tight to the wall and ceiling and matching all irregularities in the drywall). This was done by first installing the cabinets without the outer portions of the face frame attached. Then I shaped the side mullions and top rail to match the drywall and attached them to the front edge of the book case with the K-20 joiners. There was no way to clamp these parts in place, and I do not believe in nailing through the face of my projects........No worries; the K-20 will hold those parts tight forever and there is no visible gap between the face frame and cabinet carcass. The entire piece is tight to the wall and no scribe mold or crown mold was required. Try 'em, you'll like 'em.