> For the complete documentation index, see [llms.txt](https://docs.prl.one/buttonwood/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.prl.one/buttonwood/learn/buttonzero.md).

# ButtonZero

ButtonZero is a decentralized application built on Ethereum that allows for:

* Borrowers to borrow USDT at a [fixed-rate](/buttonwood/learn/glossary.md#fixed-rate-loan), with zero risk of [liquidation](/buttonwood/learn/glossary.md#liquidation).
* Lenders to deposit USDT for a [fixed-rate return](/buttonwood/learn/glossary.md#fixed-rate-loan)<br>

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.&#x20;
* **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.