Welting. Nothing special, a bit more deeper than you would do with the English welt.

Let me add a comment to 2 pics:

Never.. ever.. hold the awl like this when you sew a welt. Even the strongest thread can break once, and you will kill someone this way. You pull a thread, or tighten – this is dangerous. Don’t forget: you might work with other people, or someone just come to watch..

This is the “safe” way – in the good old times shoemakers worked in tiny workshops, so they must pay attention to each others safety. Do the same, learn the correct way.