There are two Dear Jane templates.
The triangle one is not a 45°.
I don't have mine near me right now, but I am sure that BearIsGray has it right!
The second is a square.
Both are quite helpful in trimming blocks to the perfect size.
Extra markings are there that help you centre the block before trimming.
Handy too, when lining up applique placements.
Made making the DJ so much easier .... not sure how I would have got through it without!!