Read this on another webpage, thought it was a good idea so i'm sharing it.<br /><br />I sometimes see boaters checking their trailer lights in the following fashion: One person sits in the tow vehicle while his or her partner stands behind the trailer shouting directions. OK, running lights! All right, now step on the brake! Good, now left signal ...<br /><br />Theres a much easier way: Simply turn on your parking lights and your emergency flashers at the same time. The trailer lights are two-element bulbs, so you can now see at a glance if everything back there is working. No more yelling in parking lots.<br /><br />DC