In the spring, when you have little seedlings and the sun is getting warmer... take off the tape and you can slide the top up a bit, but still keep it attached, but enough to where the "V"s are open and hot air can escape.
I cut mine the same way only I don't usually tape. If you push down hard on the top it stays put. (They work well for propagating cuttings too, which I was doing in this case). In spring, I just pull up on the top to create side windows.
Thanks Karen! You may have covered the subject before but i couldn't remember. I had a container hunt in my garage yesterday. I found a couple of juice containers that I could use. I cleaned a few containers and made all of my holes. The most difficult part of this was deciding what seeds to put in the containters. LoL