Ok....I can't seem to figure out where in the heck I keep going wrong. I've made a couple drawers to fit underneath some shelves I made. I got them to fit finally, but I am not understanding why they aren't coming together like I feel they should. If the space is 10.5" and I'm using 1" boards with drawer slides with a 1/4" profile, using a butt joint for the front and a rabbet/dado (not sure which is which) in the back...the front face should be 8" and the back 8.5" Makes sense to me on paper, the execution matches the math, but then it doesn't fit....and that's just one side...🤨

I just am not understanding why there is an extraordinary amount of fiddle farting to put them together and in the damn hole...

here's a sketch to help visualize what I mean....oh and please assume the measurements are actual and not nominal dimensions.

What in the heck am I missing?

View attachment 441157