Sometimes I need a line to be coincident, other times offset... Murphy's Law dictates that after changing a dim to zero the direction of the dimension will be reversed.
I usually get around this by using an offset. When offsetting the direction (seems to me so far) to be correct. I've noticed that you can only offset zero for entities in another sketch. That's not strictly true - you are allowed to offset to zero when actually creating the offset, but you are not allowed to change to zero afterwards (pretty pointless).
Back to the point,,
In this example I'm creating a custom weldment profile so I only have 1 sketch to work with - offsetting is not an option.
This is for a timber frame, fitted to a stone wall. When we do the survey we examine the stone wall for straightness and plumb and then allow a scribe amount in addition to the standard width. This scribe amount could vary by 2" in really old properties or be zero if for example it's being plastered in.
In the above sketch when I tried to do as I've done at the top at the bottom, the direction *always* reversed after the first time. So I thought aaah it always goes up. It did reverse on me once, but I have switched it back and forth between zero and positive values 20 times and its stayed correct. My other worry is that when the width value changes dramatically it will probably flip as well so I tried that, it seems to be working, but Sods Law states that it will wait to go wrong till the worst possible time.
Can I rely on this sketch? My gut feeling is NO. Is there a safer option? I'd like to avoid a very small offset if possible.