Tweezy

Ok create a grid, the size of which you want it to be. Then cut it up into equal increments. Each side that you want to sew needs to be 100% completely adjacent, and of the exact same size with the exact same vertices (the ones that are touching).

Take two edges of two brushes, these can sew: ][ because the top and bottom vertices are touching, they are the same length, and they are perfectly adjacent.

These can't sew ] [ because there is a gap. They also wouldn't be able to sew if they weren't the same size, or anything like that.

Keep in mind when it comes to sewing, it only matters where the BASE is, not where the "moved" displacement is. You know when you shuffle it up? The base is stlil the same, if you go into a 2d view there will still be a box that isn't really there, but it is where the displacement is registered, and THAT needs to be adjacent to the others, not what appears.