Originally Posted by Eric
I understand that you might get splinters -
I suggested that because you don't want to cut a hole for the register that is over a joist, or plumbing. By starting from the bottom up, you will know you have a clear spot underneath.
well, naturally you have to look at the situation from above AND below before ever drilling any holes.
By simply using a tape measure at various points from above and below (such as existing items, pipes, partitions,etc) the EXACT location of the openings can be determined before ever doing any drilling or cutting.