First, you would cut the proper size hole into your plenum using sheet metal snips. Next, you would bend every other tab on the start collar out 90 degrees. Then you would insert the remaining straight tabs into the hole you just cut and then bend those tabs 90 degrees to the inside of the hole to hold the collar in place. NoSheet Metal Screws are necessary with this application method. We do recommend that you seal around the connection from the start collar to the plenum with a duct sealant to prevent air leakage. Also see installation tip for Flexible Duct or Sheet Metal Duct, depending on which type you will be attaching to.