Erica, I've been making sandals since 1974. The only nails I will use are brass (or bronze) soling nails. I buy oval head ones. When I make sandals I usually use 2 pieces of sole bend back to back with Duall Cement and nails. The 11 to 12 ounce prime bends require a 5/8 nail and an anvil to roll the tip back into the sole on the bottom.
I only use the brass/bronze nails because they will not stain the leather and wear down at the same rate as the leather. There's nothing worse than to walk into someone's house wearing a pair of sandals you made and pulling a big snag out of their carpet on one of your iron nails! Well, maybe there is - cutting a big gouge out of their wood floor with your iron nails!
The down side is that the brass nails ain't cheap. They are hard to find but, you can buy them at Miami Leather - ask for Lee.
If you put heels on those sandals, you'd better get a box of 7/8's too. Nail them down from the top and roll the points back in on an anvil.
Good luck!
