To put up a shelf and, upon relative completion, have parts of the shelf remaining, whereupon they are put in to a jar. Over time the jar becomes the repository for remaining shelf bits.
Barry: "Why do you have a jar full of screws and stuff?"
Barry: "Oh right, yeah, I've got a unicorning jar myself"
Henrietta: "All your jar are belong to us"
Barry: *Haggard gasping for breath"
Eric swung the gossamer blade in a vicious arc, severing the bonds binding them. The unicorning was almost complete, time seeped away, tendrils of acrid smoke rose from the tower. The dread lord Peter had been unicorning for years, and had perfected his unicorning to an art.