Leather vests are sometimes decorated with sharp, metal pins. If you do
not want to permanently keep the pins on the vest, then using the sharp
pin used to hold the pin to the fabric is not a good idea. Large pins
can cause deep holes in the surface of leather that will never recover.
Fortunately, there are a few other ways to hold pins onto a leather vest
that are not quite so damaging to the surface of the vest. If you are
really concerned about ruining your leather vest, then you should avoid
the use of pins.
Velcro can be a great alternative to pinning pins to a leather vest. Many forms of Velcro can be purchased in adhesive form. Attach a small piece of adhesive leather to the back of the pin as well as the place on the vest where you want to wear the pin. The Velcro will be strong enough, in most cases, to hold the pin to the vest. Removal of the Velcro is simple as well. Typically wetting the surface of the Velcro completely is enough to loosen the adhesive from the leather. You can also use leather conditioner, or oil, to remove the Velcro when you no longer want it.
If you want a stronger hold between the pin and the leather, you can use super glue, or another kind of glue, to hold the pin in place. Place a ring of glue around the pin and stick it onto the leather. This works best if you allow the glue to dry while the vest is flat on a table or other surface. Allow the glue to dry for several hours. You can remove the glue from the leather safely, with oil, vinegar or a glue dissolver purchased from a home supply store (reference 2). If the glue dissolver does not state it is safe for use on leather, do not use it.
If you keep the pin closed, it can actually be sewn to the leather. A leather needle, purchased from a fabric store, will make holes in the leather that are much harder to see than holes made with the pin itself. A leather needle has a three-sided point head, and a thin shaft. This composition helps the needle glide through the leather, rather than puncturing it, leaving much smaller holes. Sew the pin on like you would a button, with only two holes through the leather. This will allow the leather to be exposed again at a later date, if you desire.