You can also set the block on the waste board, touch off of it.
Then, you do one of two things:
- If the dowels are smaller in diameter than the zero block then you move the Z down (block height - dowel width) and zero there
- If the dowels are larger in diameter than the zero block then you move the Z up (dowel height - block width) and zero there
I do this type of thing all the time when I need to stop carving a complex part and then need to recover positions later.