Take a guess?

[deadedith]

These are not 'bright' ideas, but they took me about 15 minutes to 'construct' and they do provide a service that makes a couple of processes a little easier for me. Acrylic would be better. The two light colored items are the same, only different sizes and one is a top view.

[deadedith]

The light ones - stick a pencil in the middle and draw a centerline on braces, boards up to 3" etc.

See pic for the other one - saves me trying to eyeball a ruler balanced on top of a brace or something.

[Tony_in_NYC]

I keep meaning to make one of those center line finder doo-dads! Seems much easier than the ruler balancing game.

[Ben-Had]

Just ensure your point is on center when sharpened.