4-way flashers are meagre at best, especially if you've got a trailer hitched to your truck, ergo the reason I built a
Trailer Lights Dongle (4 pics) which flash ALL the lights on the trailer. I use mine every time I back the trailer off the street and on to our driveway but also have it available should an occasion ever arise where I have to pull over to the side of the highway. If I'm forced to leave the trailer in order to seek assistance the dongle will continue to flash ALL the trailer lights as it's powered by the trailer battery, not the truck. :B