A rose shaft splint works similarly to a splint on a human bone. It supports weak or damaged portions until they are healthy enough to support themselves. Sometimes a rose is too heavy for the shaft to support its weight, and a well-placed splint can help until the shaft becomes strong enough to do so on its own. In certain cases, a splint can even help repair a damaged shaft, although in most cases, you're better off simply pruning it.
Cut the wooden dowel to the appropriate length. The dowel must be long enough to span the bent or broken part of the rose shaft, plus at least 1 inch onto the unbent or undamaged portion of the shaft on both sides.
Wrap any broken sections of the shaft with grafting tape to prevent it from becoming infected while it heals. One layer of tape is sufficient.
Place the wooden dowel splint on the broken part of the rose's shaft. Hold it in place. Wrap one piece of grafting tape around the splint and the shaft at the top of the splint and one at the bottom. Wrap more tape around the splint and the shaft along the broken sections at 1- to 2-inch intervals. Release the dowel. The splint should hold the shaft straight. If it sags at any point, add more tape.
Remove the splint at the end of the growing season, before frost sets in. Re-apply next season if the shaft droops again. If the broken section has not healed, prune it.