You will also need a pointer. A piece of heavy-gauge wire that's stiff enough that it won't bend too easily works well. Bolt it to the block and position it so that it points directly over the edge of the degree wheel. You should have already found approximate TDC, so go ahead and position the degree wheel so that the wire points at zero degrees, or TDC. From here on out, use great caution not to bump the wire accidentally.