Unsink, or sometimes just unsink, makes a concave pocket convex without fully unfolding the paper, or the opposite of an open sink. It is more difficult than the closed unsink below because there is no internal flap to grab onto to help unsink the paper, so the paper must be opened out and the area to be unsunk is pushed out (to be convex) from inside the model and from behind. It is a common fold in Lang's insects.
The closed unsink inverts a closed sink without completely opening out the affected paper. In theory, it is "just" the opposite of a closed sink. In practice, it is very difficult, because the paper being "popped" into place usually must be pulled (not pushed), and because it involves simultaneously folding over a locking flap that is hidden inside the sink. However, it is easier to manipulate than an open unsink as there is an internal flap to pull to pop the unsink in place; in an open unsink there is nothing to hold. The closed unsink appears in some complex models, such as a few of Lang's insects.
