Other ways to a saddle square

[LCHIEN]

I saw pointed out the other day that if you have a combination square set with a center finder, (like the ones pictured below)



Then the center finder with the ruler scale removed can act as a saddle square to draw lines wrapping around a 90° corner.

From sets like these:

[LCHIEN]

Also I saw it suggested to used a door hinge as a saddle square, with the hinged part on the outside. Bent to 90 degrees.