How do I secure the drain cover and frame to the ProTile™ shower tray flange?

Just fit the square frame on the round drain flange and then insert the drain cover. The system will be grouted into place. The grout joint between frame and the adjacent tile may be filled with a flexible caulk as long as thinset mortar is underneath the caulking. Otherwise, the caulking could create a restriction that could keep moisture from weeping into the drain. This would cause the shower to dry out slower than normal. You can also use ProTile’s patent pending 2mm, interlocking spacers adjust the height of drain frame and cover without cutting. Thinset and grout the drain frame and cover in place for a fast and attractive installation.