These may be either cannulated, and motor driven, or solid hand reamers.
Reamers should be sharp so they cut the bone with little friction, and should have deep flutes and a small diameter shaft. The goal is to minimize pressure in the canal ahead of the reamer, and to avoid friction and resulting overheating of bone and surrounding soft tissues (with resulting full-thickness necrosis of both!).
If the reamer is not cutting bone easily, remove it, clear bone clogging the flutes, and resume reaming slowly and cautiously.
The first reamer of a series should be shaped so that its tip cuts into the bone. Subsequent reamers need only cut against the sides of the medullary canal.
The illustration shows a solid hand reamer (left) and a power reamer (right).