I got a treadle leather belt today, and I have it on right, but I am trying to figure out how I want to punch a hole, do I want to take the belt off and punch it then put it back on?
Thank you

Yes, Take it back off, AFTER you mark the spot for the hole. Take a thin nail and a hammer and place on a piece of scrap wood or on the sidewalk and make the hole. An ice pick will also work...

Try an ice pick, if you have one. S

What about an awl??

Use a leather punch. You can either get the hammer type or the squeeze one. Either one is not that much and trust me you will use it more than you think.

I had a hard time centering the hole when I tried to punch it. To solve that I placed the belt in a crack happened to be my "sliding" tile floor and pounded the nail in. Came out great. You could use a narrow crack in the sidewalk or a board.