this may be really simple, but I cannot figure how to lock the end points of symbolic lines to the corners of a "dymanic" solid. I have a solid modeled as a duct with symbolic lines indicating an ex. There is an instance parameter for the length and width of the solid- which gives me the little arrows to select and drag the solid. But, the "ex" does not move dynamically with the shape of the solid. I am having trouble locking the line end points to the corner of the solid.
see image attached.
thanks.