Medici thesis (the dumb down version) - with v1 on the way this is what you can expect.
A regular lending protocol creates a pool and uses that to lend out. A repo "desk" has a larger build out that is layered, it requires a risk engine, settlement and oracle framework (Chainlink).
It grabs information of a stock price and it's beta risk, creates a fixed rate with a haircut % that you pay the protocol and allows you to lend out funds (which is routed through a partnership protocol).
In other words, users can take their tokenized stocks, like
$NVDA, the risk engine puts a max beta risk of lets say 7%, since the stock most probably wont move that much within 5-7 days and lends you solana:2u1tszSeqZ3qBWF3uNGPFc8TzMk2tdiwknnRMWGWjGWH for it.
If the user doesn't pay back the solana:2u1tszSeqZ3qBWF3uNGPFc8TzMk2tdiwknnRMWGWjGWH at maturity the protocol keeps the tokenized stock, if they do, they receive back the tokenized stock and pay the protocol lending fee premium.