We claim the ornamental design for a vertically mounted control knob for a gas cooktop, as shown and described.
FIG. 1 is a top, front, right perspective view of a vertically mounted control knob for a gas cooktop showing our new design in a use condition;
FIG. 2 is a top, front perspective view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a back elevation view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a right elevation view thereof; and,
FIG. 8 is a left elevation view thereof.
The dash-dash broken lines in FIGS. 1-8 are included for the purpose of illustrating portions of the vertically mounted control knob for a gas cooktop which forms no part of the claimed design. The dash-dot lines are included for the purpose of illustrating a boundary which forms no part of the claimed design.