The ornamental design for an extensiondevice for a tool, as shown and described.
FIG. 1 is a perspective top front right view of an extension device for a tool, showing my new design;
FIG. 2 is a perspective bottom rear left view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a right elevation view thereof;
FIG. 6 is a left elevation view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is a cross-sectional view of FIGS. 7 and 8.
The broken line segments are intended to represent the area where the head of a tool would be located, such as a ratchet wrench, and form no part of the claimed design.