When U.S. nuclear submarines are built, certain large items of equipment (that won't fit through any of the hatches) have to be installed before the hull plates are attached. One of these large items are white boards, used for instruction, planning and briefings on board. These items, which have largely replaced blackboards, must use special, erasable, markers. In the case of one sub, the first crew brought on the wrong markers, and found that the first items written on the white boards became permanent, and embarrassing. While it is possible, in the case of some types of wring markers, to use chemicals to get the unwanted marks off the white boards, the "wrong markers" in this case turned out to be really wrong. So every time the sub is visited by senior officers, the subs captain has to sheepishly explain that everything is shipshape, except for those damn white boards and the first stuff that was ever written on them.