First time I lit them up. I had already separated the three sizes of strands and taped them together, thinking that would be enough to get me organized in the attic. I thought I could then just pick out what size I needed based on what color hole I was putting it through and be done in no time. Not even close. I was up in the attic for all of 5 minutes before I realized this was going to be way more of a pain in the ass than I thought.