I purchased a cargo bar to go in my pickup truck bed. I can't get it to fit tight, I even tried a couple of shims of different thicknesses. Either it's too loose, and when I adjust it to be tight. I can't move the bar down to lock it to that length. Should there be some kind of fine adjustment? Looked at the instructions, nothing like that is mentioned. Based on the inexpensive price from a discount tool store, maybe I got what a paid for.