The Welt Beater is used to flatten and compress the welt after stitching by hand. A very underestimated tool by many shoemaker's. This is an indispensable tool for obtaining a flat, even welt.
Just place the beater on the top of the welt and use light hammer blows on the other side to flatten the leather welt.
The tool is massive, with a hardened head for a long service life.