First off I would question any pattern that has you make 6" blocks to be trimmed down to 4 1/2". I simply can't fathom why the designer would have so much waste. That is crazy and makes me think there is a typo in the pattern. I can see trimming down a 6" block to 5 1/2".
When I trim down hourglass blocks (like you have pictured there) I would be lining up the center of the block at 2.25" mark both from side and top to make my first two cuts (along side and top of block) using a regular ruler.
Trimming an hourglass block is much different than trimming an HST block.
Last edited by feline fanatic; 02-13-2018 at 12:21 PM.