The ornamental design for an interfittingladder, as shown and described.
FIG. 1 is a rear elevational view, broken away in the center thereof to
indicate indeterminate length, of an interfitting ladder embodying my new
design;
FIG. 2 is a side elevational view of said ladder, similarly broken away;
FIG. 3 is a front elevational view of said ladder, similarly broken away;