if it is anything like the ones in my 1984 XJ-6, there is a spring-locking piece at the bottom of the square tube/glider. Not easy to release unless you pull it very hard and then you could break something in there. Easy to get it to go in, not to come out. I think you have to fold the seat cover up until you see the mounting bracket and carefully bend the spring lock "ears" with needle nose pliers.