I have used them to show how something goes together. This is the case in which they are hard to see.
I have tried using black and they still come out looking grey.
Here is an example when I showed someone how to assemble a 3D printer extruder. I tried making them pink which made it a bit more visible but still not as obvious as I would like.
If I could make a dashed line, that would be great but I have not found a way to do that. I always find a sketch like this explains something much better than words.
I will try this and see if it helps. Thanks for the quick reply!