Good idea Donna, because it is flexible, could be molded around the lens some. Without more information or pictures this is my guess: a previous owner either didn't know how, or didn't want to take the time to correctly fix the problem which was most likely water leaking in. Hopefully the lens isn't damaged. I'm thinking the original rubber gasket is still there, and the lens just isn't seated in it right, or perhaps it's damaged. I would keep the original gasket if possible, see how the lens fits, try to determine the actual problem, and fix it somehow. Now I'm not sure if that gasket is removable or attached to the light assembly, but like I said I'm not pulling one of mine off to look. Our Uhaul
has had endless water leaks
that have drove me crazy trying to locate and fix them. I think I have it down to only one occasional leak in the left front, one time it rains and there's a leak, another rain storm and no leak, run a hose on it and no leak, ARRRGH !!! Don't know why I didn't think of the butyl tape, excellent idea.