a tailblock is a reinforcement at the edge of a board, or a rudder, skeg, daggerboard etc. Mostly made of hard-wood.

The trick is that you glue and shape this piece of wood before the lamination. So it's embedded in the final shape of the concerning part.

It will make the edge (= tail, tip, etc) more resistant for abrasion and you have created a "zone for sacrifice".

film tailblock

I used this method already for decades of years in my surfboard fins and also in my home made catrudders.