The ornamental design for a trailerjack, as shown and described.
FIG. 1 is a front and top perspective view of a trailer jack showing my new
design, the broken lines are for illustrative purpoes only and form no
part of the claimed design;
FIG. 2 is an exploded bottom and left side perspective view thereof;
FIG. 3 is an exploded bottom and right side perspective view thereof;
FIG. 4 is a rear and top perspective view thereof; and