And if you tape it into the corner of your combination square:

• the rule part of the square keeps the reference faces aligned vertically
• the nail can't tip toward one board, causing vertical misalignment
• consistent centering (or off-centering, if that's what you want)
• I find it's easier to position the rule on my layout markings than to position a handheld nail. There is a slight offset, of course, but if that's a consideration, do your layout to compensate.
• I find it's quicker, too.

If you are doing floating tenons, just mark the ends. If your tenons need to be vertical with respect to your reference face, use a long nail or screw, mark the tops, adjust the height, mark the bottoms.

If you can tolerate more offset or are willing to always layout to compensate, drive a woodscrew vertically in a long narrow block with only 2 square faces. Adjust the screw depth as appropriate. The block gives you something to hang onto without taping anything.

And now I bet you're envisioning the construction of your own dedicated jigs made from scraps and wood or drywall screws.

@MaggiWuerze@feddit.de