"tray" - the back end of a utility vehicle where you put everything. Flat bed.
Ahem--the flat part at the back of a utility vehicle is known, logically, as "the back". As in, "Put it in the back." Don't tell me: you say, "Put it in the tray". Trays are on the backs of airplane seats, or in your kitchen cabinet, and you serve or carry things on them.
Stales, you should have logged on earlier--I know you would
have told me true!