The Cardinal Gates Safety Gate Banister Post Install Clamp is a solution for those who do not want to drill holes into their banister. The clamps are not limited to the Cardinal brand and can work with other gates as well. They work well on round posts, but may not work on anything that tapers. The bolt thread size is 1/4-20, and one clamp is included in each purchase. Customers have had mixed experiences with this product; some love the adaptability for a variety of post sizes, while others feel that it is poorly Constructed and flimsy.