Safe is a financial innovation tool developed in 1980s. Its essence is the nominal forward-to-forward exchange between two currencies. One currency is called primary currency, and the other is called secondary currency. As SAFF and FRAs are both forward-to-forward contracts, there are many similarities between them: 1, and the pricing method seems to be "m× n", where m and n represent the time from the contract signing date to the settlement date and the time to the expiration date respectively; 2. Both of them have five time concepts: trading day, start date, confirmation date, settlement date and expiration date, and the relevant regulations are also consistent. Similar to FRAs, the clauses related to SAFE are also stipulated in the comprehensive agreement of recommended terms and conditions of forward foreign exchange issued by the British Bankers Association and 1989. The following is a brief introduction of several main terms:

The first contract amount (a 1)- the face value of the original currency to be exchanged on the settlement date stipulated in the contract.

Second contract amount (A2)- the nominal amount of the original currency to be converted on the expiration date specified in the contract.

Export Exchange Rate (oer)- The forward exchange rate from the trading day to the settlement date stipulated in the contract. Assuming that the original currency is British pound and the second currency is US dollar, the possible value of the direct exchange rate is 1.6000 USD/British pound.

Contract forward spread (CES)- the difference between the forward exchange rate on the expiration date and the forward exchange rate on the settlement date stipulated in the contract. Determination of the trading day of the difference between direct exchange rate and contract forward exchange rate.

Settlement spot exchange rate (SSR)- Determine the spot exchange rate of the day, and the expression of the exchange rate is consistent with the direct exchange rate.

Settlement Forward Spread (SFS)- The difference between the forward interest rate on the maturity date and the spot interest rate obtained on a certain date.