FIG. 1 is a perspective view of a string line spool, showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a right-side elevational view thereof;
FIG. 7 is a left-side elevational view thereof;
FIG. 8 is an exploded perspective view thereof;
FIG. 9 is an exploded front elevational view thereof;
FIG. 10 is an exploded rear elevational view thereof;
FIG. 11 is an exploded top plan view thereof;
FIG. 12 is an exploded bottom plan view thereof;
FIG. 13 is an exploded right-side elevational view thereof; and,
FIG. 14 is an exploded left-side elevational view thereof.
The broken lines showing a drill in FIG. 1 depict enviornental matter that forms no part of the claimed design. The remaining broken lines in the figures depict portions of the string line spool that form no part of the claimed design.