I just have a regular key lock on my shed. The handle turns down, so you have to turn it up to open the door. To lock it, you just use a key. From the inside, if it was locked, there would be absolutely no way out.
I don't lock my shed...not unless I have a reason to. I have locked it in the past, and sometimes when I have family over, I will lock it.
We are moving this summer and will be renting a house, and in that case, the shed will be locked at all times when I'm not home, as well as during the night, and possibly just all day, as well. (not sure how it will work when it's hot out, cause I can't leave the doors shut, but I'll figure something out).
Emily