Mitre box for 2020 extrusions

Mitre box to cut 2020 extrusion using hand hacksaw. Should be useful If you forgot to order a laser cutting service:)

Guides should be done from steel cylinder with 6 mm diameter. Better hardened steel and it is possible to use metal drills as temporally solution.

There are two versions of guides:

* pure cylinder guides, e.g. a drill bits may be used as temporally solution
* cylinder with cut ages (see files with "_cylinder" prefix). It's bit better because increased contact surface.