Made this Jig to help tap the ends of some various width 20mm extrusion using an m5 tap.
Added version with 4 holes. This add-on seemed sort of necessary to hold it straight without having to push the jig while tightening.
Should be compatible with 20mm extrusion from
Provided STP and STL files
Requires (2) 12mm m5 screws and t-nuts
Printing in PLA with at least 50% fill makes for a nice, rigid part.