http://formetco.com/product_the_vinyl_tensioning_bracket.php
I've used these before and love them. Easy to install/dismantle and they look great. They run around $25 each but they are worth it. I won't use anything else for anything that has a chance of getting wind behind it. I've used it for mesh and 9-10 oz banner with no problems. The link shows the entire installation process, although they have replaced the top gripper bar shown in the video with the same tension brackets now. They also supply the 3/4" round fiberglass gripper bars that slide into pole pockets along the 4 edges. It's awesome to be able just pull the pins to remove the graphic. We've also had requests to paint the galvanized brackets to match the color of the exterior of the building so that if they left them there permanently but only used a graphic there occasionally because of permitting, etc. For huge banners we insist on using this system from a liability and aesthetic standpoint. Let me know if you have any other questions.