The ornamental design for an endframe for a futon, as shown and described.
FIG. 1 is a perspective view of an end frame for a futon illustrating the features of the invention relating to the end portion in solid lines, and in broken lines to show the environment in which the invention is claimed, with the broken lines not forming a part of the claimed design;
FIG. 2 is an end view of the end frame shown in FIG. 1;
FIG. 3 is a front view of the end frame shown in FIG. 1; and,
FIG. 4 is a back view of the end frame shown in FIG. 1, taken from the opposing end of the front view shown in FIG. 3.
It is submitted that the bottom view of the end frame does not form any part of the claimed design.