And here's the version for center inlet blocks:
Essentially, it is a sqare frame on top of the waterblock. It uses two crossbars (identical in design to the previous ones) held down by two endbars. The big diffence is in the attachment of the endplates.
In the center-thrust version, the endplates wrap over the top of the crossbar, to prevent it rotating. In the frame version, the endplates attach to the sides of the endbars. This allows the frame to pivot - if one of the thrust screws is tightened more than the other, the frame will rotate and give even pressure. Don't over tighten the endplate to endbar screws!