It can be frustrating when you find a pair of sandals that fit the length and width of your feet but have ankle straps that are too short to wear comfortably. You can use a strip of leather, vinyl, fabric or whatever material matches the existing straps and sew on an extension to make your sandal ankle straps longer. By doing this, you will make your sandals more comfortable and get plenty of wear out of them.
Measure your ankle all the way around with the measuring tape.
Measure the existing sandal straps. Subtract that number from the measurement of your ankle.
Cut the strap extension material to the measurement you arrived at in Step 2, adding another half inch to the length. Also make the extension the same width as the original straps.
Thread the needle with the nylon thread, which should be the same colour as the straps. If the ankle straps are made of leather, use a thick, sharp needle.
Line up the end of the original strap end-to-end with the extension strap.
Sew the straps together. Attach the original sandal strap to the extension by pushing the needle into the original strap, then across and through the extension. Circle back and push the needle into the original strap again.
Repeat Step 6 until the two pieces of material are securely joined.
Add new holes, if your sandal straps are secured with a pin-in-hole clasp. Use the awl to carefully poke holes along the length of the strap extension.