I've been in need of a panel gauge for awhile, but I didn't want to spend $85-225 for one by Lie-Nielsen or Hamilton Tools, even though both are excellent and well-made tools.
So I bought $45 worth of brass from McMaster-Carr and figured it out on my own. Most of the credit for this design goes to Galoototron, but his site has been down for a few weeks.
I ground an old plow plane blade down to a spearpoint and it works amazingly well. Thumbsup for DIY.