In traditional markets, assets can be borrowed and sold short to gain inverse price exposure. The borrower is legally obligated to repurchase the asset in the future and return it. With the introduction of fixed debt loans in Synthetix, a shorting mechanism can be provided which relies on overcollateralization in the absence of legal enforcement. By depositing sUSD collateral, traders can borrow and short sell synthetic assets (synths). To retrieve their collateral, they must repurchase the borrowed synth and return it.