Tray collar, tray collar system and use thereof

A tray collar, a tray collar system and uses thereof are disclosed. The tray collar is made of a sheet having sections with intermediate portions connecting the intermediate portions of adjacent sections by a main fold line, at right angles to the sections, such that each section forms a tray collar wall having an outer wall and an inner wall, the inner wall being parallel and spaced apart from the outer wall, the outer wall being formed by the intermediate portions, viewed from the direction of extension of the main fold line, the inner wall being spaced apart from the outer wall. The intermediate portion has four portions, each folded in the same manner along a fold line, at right angles to a previous portion, in an opposite manner to another series of four portions so as to follow each other, a first portion forming a first spacing, a second portion extending parallel to the intermediate portion and forming half of the inner wall, extending to the center of the tray collar wall, and a third portion extendi