We have used one for several years - and they are great.
With the Morgan we just hold it up - with the black side facing the barrier - and we're straight through. Doing it this way means there is no chance of us forgetting it's there and leaving it available for the first light fingered individual at a motorway stop.
It is also recommended not to leave them in place with any car - the screen could be broken to get them.
Quentin
