I guess I'll bite - what am I looking at here?
replies(3):
There are partial holes in at at one end. You insert a small amount of dyed DNA (etc) containing solution each. Apply an electrical potential across the gel. DNA gradually moves along. Smaller DNA fragments move faster. So, at a given time, you can coarsely measure fragment size of a given sample. Your absolute scale is given by "standards", aka "ladders" that have samples of multiple, known sizes.
The paper authors cheated (allegedly) by copy + pasting images of the gel. This is what was caught, so it implies they may have made up some or all results in this and other papers.