The cover picks up several studs across the dash cowl as well.
There is a zipper down the center, to use it as a half-cover while you drive.
Also, I believe you will have to have custom tailoring done to any one you buy for your car...since it will not have the relief for the roll bar....so, you should probably have it cut, sewn and installed by a top guy.
Most all British roadsters (Triumph, MG, etc.) in that era came with a tonneau.
Had one on my Triumph back then...used it a lot when short-term parking, more to keep passing hands out of the inside. You can drive with it but...you look stupid doing it.
