Measure and calculate twice

Just about everyone has heard the proverb measure twice and cut once. I’ve followed it religiously since I started woodworking, and because of it I’ve made very few mistakes over the years. I’ve had very little time in the shop over the last couple weeks, do work and personal obligations. When I finally made it into the shop the other night, i was rushing, as I wanted to make some real progress on my current project. As I mentions in my last post, I’ve been making little plywood storage boxes. I’d just finished a box, and decided to check how it’s future resident would fit. As you can see below, it didn’t.

After several minutes of cursing, head scratching, and double checking I figured out what went wrong. In my haste, I had screwed up my length calculations. Instead of adding the thickness of the ends (3/8″) to the get the length of the sides, I added the thickness of the rabbets (1/8″). Thus I think proverb needs an amendment, Measure and calculate twice and cut once.