The threads on a tub drain can be either left-handed or right-handed, which determines the direction in which the drain must be turned to be loosened or tightened. In some cases, the drain may be reverse-threaded, meaning that it must be turned clockwise to loosen it and counterclockwise to tighten it. This is done to prevent the drain from accidentally coming loose. It's important to know the thread direction of your tub drain before attempting to remove it so that you can use the appropriate tool and turn it in the correct direction. If you're unsure of the thread direction, you can try turning the drain in both directions to see which one loosens it. If you're still unsure, it's best to consult the manufacturer's instructions or contact a professional plumber for assistance.