Please take a photo of the back end or transom of your boat. Need to make sure there are no modifications from a previous owner. First the aft mast carrier should be a two part item that is used for extending it while raising and lowering the mast. On the transom there should be two items to hold that in place the first like a big eyestrap and then the bottom piece, retainer, that you should see around the top of the lip or the hull to deck joint near the bottom of the transom. Please take a photo and post.