PCB Trace Orientations
It's usually a default snap to that angle in the EDA software we use to lay out boards. It can usually be overridden, but there is seldom a good reason to do so- 45 degree angles do the trick and keep things neat. It's also easier to keep the spacings within rules when endpoints snap to a certain grid when you only have to deal with the grid itself (parallel traces that are vertical or horizontal) and spacing on 45 degree angles of 0.7 times the grid (parallel traces that are at 45 degree angle relative to the X or Y axis).