No sweat - it's better than my videos.
In the days before Intent Manager it was often a challenge when nearly vertical or horizontal line segments were required. One would have to exaggerate the slopes to get the correct constraints and then change the dimensions to the desired ones. The bad news was that if there was a need to revisit the sketch, if one didn't re-exaggerate the values, Sketcher would re-evaluate the sketch and force the undesired constraints on the items.
The stupid thing was that Sketcher wasn't looking at the slope to determine the need to force the constraint, but at the apparent screen coordinate offsets, so if one zoomed in far enough the apparent offsets would increase and over-ride the automatic horizontal/vertical constraint.