crosshatching
Crosshatching is a monochromatic shading technique that uses parallel drawn lines of a uniform strength at different densities to simulate varying levels of brightness; thus a lightly colored object will have few to no lines, whereas a very dark object may have so many lines as to be solid black. Crosshatching is a compounded variant of simple hatching and may have two or more directions in which the lines lie.
For when a newborn animal breaks out of an eggshell, see hatching.