PattyorCraig, If your sheetrock is going to but your timber I agree that J mold is the way to go, there are two styles of J mold that I have used, standard "J" and tapeable. The end result with standard will show a small 1/2" beed weather you use metal or plastic. Tapeable will give you a cleaner and more pleasing end product.Before installing the sheetrock and J beed put 2" wide "Blue" painters tape on the timber so that the edge of the tape will be 1/8"-1/4" behind the edge of the j mold. When you spread the joint compound the tape will prevent the joint compound from sticking to your timber. After each application of compound run the point or edge of your knife down between the tape and j bead. This will give you a 1/16" crisp, neet, and fine line,that will always look great even after the sheetrock and timber dry and shrink.Try not to leave the tape on too long, it may be more difficult to remove, Good luck, John...