I've never used one.
I've thought of getting an inexpensive wood carving chisel cut to 90 degrees.
Currently I use a small metal machinist square...........I think Micro Mark shows one....... and VERY sharp NEW number 11 blades and work along the square from each window corner. I can do a complete structure wall layout with window cut outs in about an hour. The trick is to use the square along the outside edges of the structure before roof angles are cut and wall are stood up. Mostly I use Grandt Line castings and they have a location on their website with the exact dimensions of the rough openings necessary for all of their doors and windows; given in thousandths.
"A person who spells a word only one way lacks imagination." Mark Twain