Would appreciate some advice on a few bass guitar queries. I've been looking at basses for sale (on ebay!) and found a question there, buyer: "Is the neck straight?" Seller: yes! Well ok if the neck is obviously warped it's easy to see - but "straight". How does he know, other than just by looking at it? Is there a better way to check. buyer: "Truss rod adjustable at the body". me: Why is the truss rod adjustable? What is the usual reason/procedure for doing such an adjustment (other than a replacement neck)? I thought the truss rod was to lock the body to the neck and that was that - do they work loose over time? Thanks, and sorry if these are stupid questions.