I made a discovery a little while ago. That is, most plates and tiles can slide in the straight grooves of what are known as garage door bricks. These are mostly 1x2x1, 1x2x5, 1x4x1, 2x2x1, and a long 1x14x1 with curves to go from vertical to horizontal. Well if plates and tiles can slide through, they must be about 3.2mm. Which means that the little guide pegs on the side of the garage door panels must be 3.2mm. And if they're 3.2mm, they're essentially a bar.. Awesome, next question, how far apart are those bars? The obvious choices would be 3 plates, as in stacking headlight bricks, or 2.5 plates as in a brick width. Oh, and how long are these things?
Turns out that my second try with some headlight bricks was right on. I tried stacking them but it was clear that these weren't at 3 plate offsets. I then set the headlight bricks side by side and everything worked perfectly, even the length. This means that 1x1 bricks with a side stud are not going to work. You'll end up being a plate longer than 10 studs.
Now I want like 1000 garage door panels.
