I've been using solidworks for ~4 months and this is a problem I encounter constantly, and one that is very easy to diagnose/fix in Pro/E.
Here I have a spline that is copied from another sketch, in this instance it needs to break off halfway down. I drew a line across the spline, trimed the end of the spline I didn't need and trimmed out the line itself. Ideally the entire spline could be left in place and half of it turned to construction, but I'm not sure how to do that (trim to construction geometry)?
At any rate, I drew in a a second spline coming in from the right in the screen captures, to intersect the new endpoint for the first spline. SW indicates that these two points are coincident. However, it fails check with a 'Two Points Gap'. When I zoom in tight to see the gap, I get a bunch of zigzag lines rendered that were never a part of my input and cannot be selected/deleted. Sketch is included in part file.
By the time you read this I will have worked around it, but I'm looking for some tips for how to prevent this constant frustration. Surely I am doing it wrong! Thanks.