Turning a screw clockwise tightens it; turning it counterclockwise loosens it.
Tips
memory
顺 'following, with' + 时针 'hour hand': moving the way the clock hands go. The opposite is 逆时针. It usually comes before 方向 'direction' or before a verb such as 转 'to turn'.
culture
Buddhist pilgrims in Tibet walk clockwise around temples and holy mountains, a practice called 转经; followers of the older Bon religion go the other way.
