I have this one and I love it! If you look at the you can see how you can position it different ways, including the U-shape you talked about. It's made of metal so it has a little weight to keep it sturdy, but it's light enough to move and set up easily. It's good sized but the rods are only about 2" apart so it keeps are little ones safely contained. The latch is easy to reach at the top - it just lifts up to release and the lowers to relatch. AND the best part is that Petsmart has it on sale for a really good price right now.
Sorry - I know I must sound like a salesperson! But I've had mine for a couple of years and it's one of the best investments I've ever made.
Good luck in your search!
Bonny
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He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion. -- Author Unknown