I just completed a simple garden bench, made of nothing but 1X4s with 2X4 legs... perhaps the simplest project one might find on the 'net for "wooden bench." When I finished the rectangular frame upon which the slats that form the seat are attached, the darn thing would not sit flat on a flat floor. This was just a rectangle of 1X4s. No seat slats yet, no legs. Yet the darn thing was not flat, and square. (and I had clamped it all before screwing it together.)

I kept thinking, "now how could I screw up something that simple???"

I went on and attached the slats on the top... the whole thing just sort of wobbled like a potato chip... hmmmm Just a bit flatter.

I then attached the simple 17 inch long legs... carefully measured and cut. I could feel merely a paper thin difference in the length of these soon to be legs for the bench. Well, give it a try.

I screwed the legs onto the bench, and sure enough, it wobbled... had nearly an inch of gap between one leg and the floor... this bench wasn't going to sit still. I had carefully measured everything. But something in my assembly technique had thrown the core frame out, and the end result was a wobbly bench. So I eyeballed the gap difference in the leg to the floor (it would have taken a bunch of coasters or napkins to take out that wobble). With that eyeball measurement in mind, I trimmed one leg down.

The darn bench works fine now. The eyeball measurement was perfect. (or "perfect" enough). I always have had a hard time putting two boards together. I can't imagine trying to build a house.