Yes. The large metal piece at the top of your panel is a U-bar, and the small lip at the bottom is the rib mentioned in installation instructions. The WD-339621 operator bracket attaches to both for a secure fit.
You can safely screw into the U-bar on the top of the panel and into the bottom rib as shown in the installation diagrams.
Shop WD-339621 Operator Bracket

U-Bar Placement

Rib Placement
