I tried posting a picture but it won't let me. I need to replace my light, and I have watched enough videos and I am proficient with electrical work but my problem is removing the black top to the junction box. Outside my pool cage, right behind the light is 3 gray pieces of conduit about 18" tall with a black cover. I removed the four screws in the corners but the lid won't come off. I don't know if there is a rubber gasket that has maybe melted, like a weld. Maybe it is caulked shut? Any suggestions?