its stowed position and locking position or by other means when in its locking position of fig3 the rearward end 90 of locking device 86 engages a stop 93 secured to the inner side of lower panel 68 when in its locking position locking device 86 maintains the unit 34 a in its deployed position a flexible sheet member 94 is secured to the outer side of door 20 the first side edge 42 of upper panel 36 the first end edge 58 of intermediate panel 52 and a first side edge 76 of lower panel 68 by any convenient means to close the outer side of unit 34 a when unit 34 a is in its deployed position unit 34 b is a mirror image of unit 34 a and will now be described with u201c u2032 u201d indicating identical structure on unit 34 b unit 34 b includes an upper panel 36 u2032 having a first end 38 u2032 a second end 40 u2032 a first side edge 42 u2032 a second side edge 44 u2032 an outer side 46 u2032 and an inner side 48 u2032 the first end 38 u2032 of upper panel 36 u2032 is hingedly secured about a horizontal axis to door 20 by a hinge 50 u2032 the numeral 52 u2032 refers to an intermediate panel having a first end 54 u2032 a second end 56 u2032 a first side edge 58 u2032 a second side edge 60 u2032 an inner side 62 u2032 and an outer side 64 u2032 the first end 54.