Do I need a chain guard for transporting a chainsaw, and how should I secure it?

Yes, you need a chain cover (scabbard) and it must be tied down — no free rides in the truck bed. Most states require a scabbard for transport, and even where it’s not law, it’s stupid not to use one. A loose chain can flip the saw or start cutting whatever it touches. Also tighten the gas cap to prevent fuel spills; in a truck bed, strap it upright.