This is what I came up with for a DIY spade on my pallet forks. It works pretty good, does a really nice job on enticing multiflora roses out of the ground as well as making a trench.
I came up with this to get away from a chain and binder to use the receiver and a hitch pin.
Pockets for the front of the forks.
Made with 1/4 inch plate I had laying around, has a lifetime warranty too.