The ornamental design for a sandal, as shown and described.
1. Sandal
1.1: Perspective
1.2: Front
1.3: Back
1.4: Right
1.5: Left
1.6: Top
1.7: Bottom
The sandal comprises a sole with heel and an upper comprising several transverse straps; in the part of the upper which in use rests on the instep, on the outer side, two pairs of alternate straps are interconnected by a respective longitudinal flange, so as to form two interwoven H-shaped patterns; the reproductions of the design show a right sandal, the corresponding left sandal being a mirror image of the one shown in the reproductions.