My trailer jack's handle vanished during a short drive, presumably lost its one bolt and bounced off down the highway.

This version uses two steel bolts, one through the jack's screw and the other as a handle, and uses nuts with nylon inserts.  It's sized to fit 1/4 inch bolts and a Lowe's bROK brand trailer jack, but the OpenSCAD constants could be changed to work with anything. 

The body flares near the jack itself to shed rain better, and it uses internal ribs to print with less plastic (70 grams) but still be strong.

Uses two 1/4-20 bolts:

• A shorter crossbolt (2"?) through the existing hole in the jack screw.

• A longer handle bolt (3", preferably stainless) pivots freely at the end as a spinning handle.

Both bolts are retained by 1/4" nuts with nylon inserts ("nylock"):

• The short crossbolt's nut fits into the hex hole in the handle. The crossbolt should be tightened carefully by hand, since the printed hex cavity won't take much torque (and the whole print would just crush if you tighten too hard).

• The long handle bolt's nut is captive in its slot. I designed it so the handle bolt can spin freely, so you can just grab it and spin, which worked satisfyingly well!

Might need a coat of paint to resist UV. If you live in a hot place it probably needs to be a heat-resistant filament, I used PETG.