How to dimension a slot in a drawing?

Slot centerlines, center marks, and callouts slot drawing callout The standard omits the word SLOT from the callout, and states that the end radii are to be indicated but not dimensioned RE: slot call out slot voor houten poort I am trying to grasp the concept of the round slot position callout I have to check part against the drawing where hole is datum B

slot rock One for the slot center marks and one for the dimension callout 80% of all what I do ends up being sheet-metal with almost every bolt hole