# ButtonZero ButtonZero is a decentralized application built on Ethereum that allows for: * Borrowers to borrow USDT at a [fixed-rate](https://docs.prl.one/buttonwood/glossary#fixed-rate-loan), with zero risk of [liquidation](https://docs.prl.one/buttonwood/glossary#liquidation). * Lenders to deposit USDT for a [fixed-rate return](https://docs.prl.one/buttonwood/glossary#fixed-rate-loan)
The Buttonwood Tranche protocol can create fully-collateralized [zero-coupon](https://www.investopedia.com/terms/z/zero-couponbond.asp) bonds with zero-liquidations and zero margin calls. These bonds are very configurable and have the following **parameters**: * **Collateral asset**: The asset backing the bond. Its volatility generates the risk that senior tranche holders transfer to junior tranche holders. * **Maturity date:** These bonds *mature* at a certain date, after which the *collateral asset* is distributed among the borrowers and lenders. * **Tranche ratios:** These define the way that risk is transferred from more senior tranches to more junior tranches. They are generally denoted in terms of percent, i.e. a "20/30/50" bond represents a 20% A-Tranche, 30% B-Tranche and 50% Z-Tranche. This in turn means that the A-tranche holders are entitled to the first 20% of the value. After the A-Tranche has been made whole, the B-Tranche holders receive the next 30%, with the remainder going to the Z-Tranche holders.