“I'm not sure how these have got such positive reviews. They look okay, but as someone else mentioned, you can only attach one connector to one aluminium piece, with the screw. They don't fit the the aluminium pieces on the other sides well enough to qualify as "push fit". Trying to assemble a simple frame or box with them is a complete non-starter - the pieces just keep falling apart. The only way they might work is to use glue.
I don't know what the manufacturer's intention was, but these are very close to being useless, as I see it.”