CE Smith Post Guide-Ons 60 - Black CE Smiths boat trailer guide-ons make it easier to see the end of the trailer while on the road or when loading or unloading. The guide-ons protect your craft from damage and provide an additional measure of safety while trailering as they provide a visual aid for other drivers. The Post Guide-On is designed with square 16 gauge steel uprights, pre-galvanized for corrosion resistance, and 2-38 diameter. It also features a black PVC posts to secure its stance fo