Updated after a week's use: I have relocated 12 squirrels since receiving this incredible trap a week ago. I trapped 3 last Sunday morning alone (granted the trap was positioned beneath my friends bird feeder, which had become squirrel central). I captured another 9 from my yard (two a day has been pretty common). Those reviews that say the trap won't close must have either received a defective one or, more likely, don't understand how to set the trap door's latch. I've added a picture. The latch (the instructions call it the "pot hook") slips beneath a rail on the door from the back. Very little pressure on the plate will trip the trap's door. Once closed there's a sturdy bar that keeps the door firmly locked. No way can it be forced open from inside. The cage is incredibly rugged. The medium size is perfect for the squirrels in my yard, but I doubt this size would work for chipmunks. Other reviews have noted that opening the trap door to release your "trappee" is a bit hairy since you need two hands to compress the spring that holds the door locked, then you need to keep the spring compressed while lifting the door. I created a "C" shaped clip bent from a length of finishing nail which loops around the spring locking bar and a rail on the door and keeps the spring compressed so that both hands are then free. I attached a short wooden handle to this clip. The opening in the "C" clip is around 1/2 inch. The handle allows me to install this clip with one hand while holding the spring compressed with the other hand. The release procedure, which, after 12 critters I have now gotten down to around 1 minute, goes like this:- carry trap in my IKEA bag to the squirrel resort I've started at a nearby pond (located 1.5 miles away which I assume is far enough?)- tilt trap to vertical position with door at top and critter on bottom- compress door spring. Two hands are needed to start, one to compress the spring and the other to slide down the spring locking bar. Once the spring is flat against the door you only need a single hand to keep it compressed.- Using free hand, install C clip on spring and door to keep spring compressed.- lift door lip slightly and attach large spring clamp (shown in picture. Home Depot sells these for $1) to provide additional handle when opening door.- tilt trap towards horizontal and, at about the 30 degree point, open the door.- at this point the trap will suddenly become unoccupied. I've only had one that needed only the slightest encouragement. The other 11 were furry gray streaks.So, the good news is this trap works well ... that's also the bad news since I'm getting a bit weary of this new career as a squirrel UBER driver. In fact, I just took a moment to check my trap to find yet another occupant. So this is the 5th day since starting this project that I've had a double occupancy day, ... so the count's now 13!Original review:This trap is the bee's knees, and the squirrels' scourge . Simple to assemble, a little tricky to set, but boy did it work FAST. Caught first of the obnoxious pests the first day out. A few peanuts inside near the back and a couple outside as lure. I haven't had a chance yet to transport and release my first victim so I will update this review a bit later with how this goes, I will also add a few pictures and comments regarding how to set the trap-door correctly since there are too many negative reviews that incorrectly report that this trap doesn't work. Most likely this results from not understanding how to engage the trap release arm. When done correctly then the very little weight is needed on the release plate. The negative review that says "hook holding door does just that... it holds the door open and the trap can not activate" has clearly not understood how to arm the trap. I'll add a picture showing the trap armed since the instructions included were not very clear on this point. The trap comes collapsed (in a flat carton) and assembly is simple. Only one side opens, and there are clips included which you can use to firmly latch the back fixed door in place. There's a locking arm that's used to keep the trap stable after assembling and I used some wire ties at the bottom to make sure this arm stayed put. I also have one of those large nylon IKEA tote bags (called FRAKTA) which is the perfect size to carry the assembled trap with it's occupant during the deportation process. Once the trap is occupied this bag also works to provide the incarcerated critter with some stress relieving solitude until it's relocation time. These bags come in bright neon orange too, but the blue seems more soothing.