It is a good idea especially when dealing with aggressive fast animals. But not everybody keeps there T's in small enough containers to do that.... Sort of like your big T' like H.Shmidti, Serecopelma Generala, L. difficilis...etc. But on the cobalt all you have to do is gently oped the lid, be careful not to breathe on her or make any sudden movements, gently place a 32 ounce cup over her and slide the lid under to secure the T. As you get more acustomed to this hobby and comforatable you will see that this technique works on every tarantula in the hobby....... Even the arboreals.