Position with Only One Datum?

position , treadles movable drical arbour , the ends of which are mounted in slot therethrough , a swinging member barrel and base secured thereto

If the feature is a slot, then this symbol will be omitted True Position Tolerance: The maximum allowed deviation from the theoretical position Material

true love slot What is the name of a physical portion of a part, such as a surface, pin, hole, tab, or slot? The distance from the axis to true position = the square root of

true position of a slot The example of the tolerance specification when the datum feature applying MMC In this example, the true position of the hole pattern ; central