What the lease is actually for
If you don't have your own MC authority yet, you run under a carrier's authority instead, and the lease is what makes that legal. Part 376 exists because the person signing it is usually the one with the least leverage in the room — one truck against a standard-form contract written by someone else's lawyer. The regulation doesn't set your split or your rate. It sets what the paper has to disclose, in writing, before you're bound by it.