/usr/include/X11/bitmaps/grid8 is in xbitmaps 1.1.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | #define grid8_width 8
#define grid8_height 8
static char grid8_bits[] = {
0x55, 0x00, 0x01, 0x00, 0x01, 0x00, 0x01, 0x00};
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