Filler - extension pack

This remix adds the symmetric "hold guide" so you can use it as a side feeder easily. I also added some simple remixes which can be useful for stacking multiple rollers.

I think it is easier to print and less problematic to reuse than most of the other one-pieced designs.

Optimal build is
- 2x symmetric holder,
- 2x roller (from the original design),
- 4x 608ZZ (from the nearest skateboard shop),
- 2x parallel brace.

"I have a lot of place" build:
- 4x symmetric holder,