I never noticed this little button on the top of my Up-lula until this morning and that it will lock the thing closed. I was at the range and while loading, all of a sudden my up-lula wouldn't open back up. I couldn't figure it out until I took the second one out of the bag to finish and noticed that it has a lighter colored button and that the first one was pressed in. Is there a reason to lock it closed? hmmm