Whether there is a shut-off valve depends on the chassis year and model. Many do NOT have them.
If the fuel line is a flexible hose, a common mechanic trick is to pinch-clamp it with Vise Grip pliers. The chassis or engine manufacturer probably won't recommend that because it is possible to damage a hose that way, but it is a common technique anyway. Just don't get carried away!
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL