A price that a futures contract may not exceed or drop below on a given trading day. For example, if the lock limit is $25 for a given contract and it had previously been trading at $22, the exchange will not allow the contract to trade above $25. Likewise, if it were previously trading at $28, it would not be permitted to trade below $25. Futures exchanges set lock limits in order to protect investors from the excessive volatility often involved in futures trading.
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