Answer:
well, do you mean like the pegs on violins and violas? If you are, see if iy has any kind of a screw on the side of the peg. If there is, just get a screwdriver and tighten it. That's what I do with my violin sometimes, and it works. No guarentees on yours though. If there isn't a screw, you might want to take it into a music store to have it tightened. Dont try anything by yourself. Trust me, it wont work