240 within the frame 232 is a sliding window 242 and a fixed window 244 attached to the sliding window 242 is a mechanism 246 for locking the sliding window to the forward side 238 of the frame 232 the sliding window 242 is mounted on an upper guide 248 and a lower guide 250 the upper and lower guides 248 and 250 allow the sliding window to be moved in a longitudinal direction so that the window assembly 228 may be opened and shut the sliding window 242 and fixed window 244 include an outer pane 252 of tempered glass and an inner pane 254 of heat strengthened laminated glass formed between the outer pane 252 and inner pane 254 is an air gap 256 the frame 232 includes a flange 258 which extends generally horizontally inward through the sidewall 18 integrally attached to the outer end of the flange 258 and extending generally vertically outward from the flange 258 coplanar with the exterior surface of the sidewall 20 is a peripheral skirt 260 rigidly attached preferably by welding to the outer surface 258a of the flange 258 and extending along the upper side 234 lower side 236 and rearward side 240 of the peripheral frame are tap blocks 262 on the forward side 238 of the peripheral frame 232 the tap block 262.