Strictly speaking, all Panama chock, EU type chock, NS type chock are all closed chock according to their shapes. But here this chock is only called closed chock. Its function is similar to Panama chock, to let mooring rope pass through. Due to closed chock has wider hole, it can be used on port, boat, or barge but seldom used on world sailing commercial ships because its SWL is not big as most Panama chock. And the material is often stainless steel, bronze, or cast steel. When there is closed chock, there is of course open chock comparatively.
