1965-1968 How does convertible top boot attach to rear seat? Velcro or slider? Bonneville Catalina

I'm trying to identify some convertible top information, and I am specifically interested in how the convertible top boot attaches to the rear of the back seat - with either velcro or a slide-in bar. I am specifically interested in 1965-1968 Bonneville and Catalina (or even other 1964-1968 GM B and C). If you have a 1965-1968, how does your boot attach to the rear of the back seat - with a slide-in bar, or velcro? I'm pretty sure 1964 and 1969 Bonnevilles had a slide-in bar, but I don't know about 1965-1968. Let me know the year. Thanks.

We are about finished restoring a '67 Bonneville and its boot attaches to the back of the rear seat with a sliding bar.