Post caps are decorative tops that can be attached to the top of rail posts to add a customized look. Some deck builders bevel the tops of the rail posts themselves to soften the sharp corners for a stylized finish. You can choose from hundreds of pre-manufactured post caps made from wood, metal, composite, glass and ceramics. Some are very detailed and interesting, while others are playful (we're talking squirrels and cherubs).
Post caps are not for everyone. However, they can offer a nice option for deck projects that seem to be missing something. Some rail systems don't even allow you to use them. Even wood rails require you to install taller rail posts. Some builders fasten a 4x4 block to the top of post caps to allow for a continuous rail cap.
Post caps can be attached in a number of ways. Some post caps can be delicately nailed in place. Glue works well for others. Remember, post caps will probably be touched by any and all passing people. Over time, the post cap is bound to loosen up. We have even seen post caps blow off of decks during heavy winds.