Corner block
FIG. 1 is a perspective view of a corner block showing my new design, the broken lines showing a window frame and three additional corner blocks are for illustrative purposes only and form no part of the claimed design; 
     FIG. 2 is an enlarged perspective view thereof; 
     FIG. 3 is an enlarged front elevational view thereof; 
     FIG. 4 is an enlarged left side elevational view thereof; 
     FIG. 5 is an enlarged right side elevational view thereof; 
     FIG. 6 is an enlarged top plan view thereof; 
     FIG. 7 is an enlarged bottom plan view thereof; and, 
     FIG. 8 is an enlarged rear elevational view thereof.