Replacement Knob for Man Ship Stainless Steel Portlights Black Nylon Knob Keeping your portlight dogged down is important to create that watertight sealant Replace your Black Portlights Knobs/dogs for Man Ship Stainless Steel Portlights. Keeping your portlight dogged down is important to create that watertight sealant. We also offer the cross roller pin if that is in need of replacement. This roller pins also used on the portlight hinges.