I think whoever left it there is trying to say "nothing really mattress anymore".....................

That is an audacious pun, Keith. Which I liked.

....or it could be a tribute to spring.

Oh dear..............

For rent but with no mattress !

Unless you ttake this one, Léo. I used to know a fellow who furnished his entire house with furniture left out for garbage pickup in this neighbourhood. Of course, mattresses in Toronto often have bedbugs. so it's probably wiser not to take one.