The ornamental design for a cornerclamp, as shown.
FIG. 1 is a front elevation view of a corner clamp in accordance with a first embodiment of my design;
FIG. 2 is a rear elevation view of the corner clamp of FIG. 1;
FIG. 3 is a top plan view of the corner clamp of FIG. 1;
FIG. 4 is a bottom plan view of the corner clamp of FIG. 1;
FIG. 5 is a left side elevation view of the corner clamp of FIG. 1; and,
FIG. 6 is a right side elevation view of the corner clamp of FIG. 1.
The claimed design is shown with a symbolic break in its length. The appearance of any portion of the article between the break lines forms no part of the claimed design.