I use locking hitch pins on the tow bar.
And I lock the hitch too. I would 'never' tow a toad or anything for that matter with just those pull pins most of the tow bars come with. Nor do I ever use cotter pins on a hitch. It's locking hitch pins all the way!
Many locking hitch pins come with plastic covers which keeps road debris and most of the water out. A must if you use them up north in winter/salted slush roads. So far so good 7 years and counting.
These are pricey but IMHO worth it because you can lock and unlock with one hand one key no fumbling. Push it and it's locked back in place. All three keyed alike.
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