I like to secure the drain plug for my trailer boat near the drain hole itself with a section of coated wire leader secured to the outboard motor bracket. This way I never lose the plug, and when I do a walk around before hitting the road, it reminds me to put in the plug if I have not done so already. If I happen to forget and launch the boat without the plug (which happened to me once), I can reach over the transom, grab the plug, and insert it. That’s better than racing about trying to locate the plug while the boat rapidly takes on water.