inverting one tray with respect to the other the bar and claw 34 changes sides 34 and these members remain co operable along the sides opposite the hinge portions there are provided a pair of interengaging clips 16 which engage as best seen in fig3 the clips are identical but one clip faces upwardly and the other faces downwardly and the interengagement is flange 17 which projects from the side of the tray each clip 16 having a projection 18 which snaps over the flange 17 as seen best in fig4 the end walls of the trays 11 are provided with recess flanges 19 which when the trays are closed together provide an access opening 20 into which a patient can insert his hand each tray 11 also has infill of soft resilient open cell polyurethane foam 22 which will conform to the shape of a patient 39 s hand each foam infill 22 has greater depth than its moulded tray 11 thereby leaving a gap 21 between side walls of trays 11 limiting danger of damaging a patient 39 s hand two films are placed one over the foam of each tray and the edges of the films are retained to the side edges of the applicator by means of retaining clips 23 which are best seen in fig3 and 4 each retaining clip 23 comprises a hinge member 24 which resiliently engages an outstanding projection 25 extending part way along and outstanding from a wall of a tray 11 the hinge members 24 hinge on hinges 26 the shapes of which are somewhat similar to the.