where is the release to extend the bar

It's part of the handle mechanism. When the handle is in the full open position,the ratchet mechanism disengages and allows the smaller tube to slide freely in and out of the larger tube.

Thank you for your question in regards to the Adjustable Cargo Bar. Please note that the location of the lock and release is the item that looks like a handle. That is where your locking and release mechanism is located. Any additional questions please let us know. Thank you. Victor T. - CargoSmart Customer Service