Printrbot thumb saver & cable retainer

In order to change filament spools on the Printrbot Simple Metal, the operator must squeeze the filament release. Its contact area is small, resulting in discomfort on the squeezing thumb or finger.

An unrelated nuisance is the cable bundle on the left side, which dangles on the build plate, occasionally getting snagged on a print in progress.

In the spirit of "two birds with one stone", we remedy both issues with this combination thumb saver / cable retainer.