Meaning of "Keel docking"

In dry docking, the weight of a ship is carried almost entirely on the keelson provide the means of distributing the pressure on the center line and docking keels composed of doubling strips of plate or built-up girders are sometimes fitted on the bottom at a distance from the center line corresponding to the best position for the bilge block. The docking keels are fitted in a fore-and-sft direction, generally parallel or nearly so to the keel.

Keel docking Meaning of