The ornamental design for a retainerstrap, as shown and described.
FIG. 1 is a top, front, right isometric view of another embodiment of an ornamental design for a retainer strap;
FIG. 2 is a top plan view of the retainer strap of FIG. 1;
FIG. 3 is a bottom plan view of the retainer strap of FIG. 1;
FIG. 4 is a front elevation view of the retainer strap of FIG. 1;
FIG. 5 is a left side elevation view of the retainer strap of FIG. 1; and,
FIG. 6 is a right side elevation view of the retainer strap of FIG. 1.
The ornamental design that is claimed is shown in solid lines in the drawings. The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design. The dash-dash-dash broken lines in the drawings are included to illustrate unclaimed surfaces or environment of the claimed design. The dash-dot-dash broken lines in the drawings are included to define unclaimed boundaries of the claimed design. Back elevation views are excluded from the drawings as being identical to the front elevation views.