Let's build a corral in ordinary 3D. A circle encloses the maximum amount of ground for the amount of material used to build it. To build one, you first draw a big circle on the ground. Set posts into that circle at regular intervals. Connect the posts with slats. Done.
In 4D you draw a sphere on the ground. Set posts into that sphere at regular intervals. Oops, that is only possible with certain numbers. The only real possibility is twenty, but that might be too small. So what should 4D ranchers do?
When building it is always desirable to have standardized parts. We want all the slats to be the same length. We usually can't do that, but maybe it is possible to have two standard lengths. Anyone know how?