I have a thule rack question?

how do i take off the strap so i can attach it to the sidebars? like the crosspiece not the actuall snowboard rack http://www.thule.com/en/US/Products/Snow鈥?/a>|||there are two ways that I came across of taking them of. The cross piece should have a lock on it. Unlock it and slide it forward. The other kind I came across it appeared that there were no way to move it or any other way to remove it. I had to bring it to a small mechanic shop and let them figure it out.