Stack the two ply pieces and drill holes where you marked them. Then clamp the ply onto the shovel with 4 (or 6) bolts, fit the second handle in wher...
Never bend over again to shovel snow! Add a second handle from any broken tool with a D-handle (or even a cheapy shovel cut off), two pieces of plywood and a few nuts and bolts. It works even better than those expensive curved handle shovels you see in the store.
Step 1: A little prep
Cut two pieces of scrap ply approx 9x16", cut a handle down to about 20" long, buy six bolts, washers and nuts the appropriate length for the thickness of the second handle and two pieces of ply, typically 3 inches.