This invention provides the correct Viterbi decode traceback starting index is obtained for all constraint lengths and frame sizes. Said contact termination consists of at least one elastic contact blade comprising a blade which is connected to the rear of at least one ceiling element and which extends towards the rear before folding. The keeper member automatically engages the first keeper pin when the first tonneau section is pivoted into the closed position and automatically disengages the first keeper pin when the first tonneau section is pivoted into the open position. Fast spatial alignment may then be performed and accurate video quality measurements made.