Just a handle, no shoulder strap or way to attach one really. I'd say the locking mechansism is pop and go. You have to push down on a button and pull up on the handle, which is the only reason it's tricky to do one-handed. Not difficult. All the mounting hardware is very adjustable, so you can align the stops around struts and get the hook placed "not too loose, not too tight".

Worst case, you can just take them back. After all, it is REI.