I have recently discovered a new piece of hardware for use with leather: The leather staple. They resemble a regular staple used in a stapler for holding papers together, only wider and with super sharp points.
I have drawn blood more than once from handling them, and I suggest you treat them with respect.
In order to try them out I made this cap made of 4 - 5 oz. veg tan leather. Since I like to make things that look old I photoshopped the cap into a 19th century photograph.
Our plague doctor masks have a dart on the bottom of the beak, and on both the Krankheit (shown below) and the longer Schnabel that dart is closed by means of a strip of leather that goes on the inside of the mask attached with two rows of rivets.
Unlike rivets, the two pieces of leather being attached do not have to overlap. In fact the legs of the staples are so short (about ¼") that unless the leather is really thin you can't overlap them. Instead I used them with a the two pieces butted up to each other.
After playing around with the leather staples it occurred to me that they could be used to close up the dart. In the photo you can see the old way with rivets on the left, and the new way with staples on the right. I think it is an improvement, and will soon be converting our patterns over to use the staples.