zip-out rear window

[Ryan van Luchene <Ryan.van.Luchene@celeradiagnostics.com>]

i had a new vinyl top w/reflective strips and Z.R.W. installed on my TR6 
about 3 years ago. I'd like to unzip the window, but don't know how to 
properly hold the window when it's rolled down. My top doesn't have a 
strap or anything to hold it down properly (which i have seen in an 
illustration in the official driver's handbook). Is this something that 
you have to custom install? 

Ryan
71 TR6