Latch marks are marks on either the blade, the handle, or the latch itself as the result of contact during balisong manipulation. Most current balisongs use either spring latches or latch gates to address this problem, but oftentimes older balisongs do not have these useful features. Forumite Slick (a.k.a. anyone) came up with a very simple solution using rubber o-rings to prevent the latch from contacting anything else during manipulation. As you can see in the photo, the addition of two o-rings to the latch post keeps the latch from contacting the rest of the knife and will easily be out of the way when the knife is latched closed. In this particular case, size R03 o-rings were used but the needed size may vary depending on the size of the latch.