Vertical Pin: Here is an example of a vertical pin and rescue: Vertical Pin & Rescue.
Center Broach Pin: This is basically getting stuck sideways on a rock, tree, or stump. Diagram 5.15 in this book shows an example: Center Broach & End to End Pins.
End to End Pin: Basically both ends of the boat get hung on separate rocks and the center is free but pressed downstream by the water current. The diagram from the book in the center broach pin also has this one.
Pinch Pin: This is a very nasty (but rare) pin. Basically the front of a pointy kayak gets caught in some type of rock crack. The boat then is folded downstream and held in place by the bend on the boat.
Flat Pin: Flat pins are a relatively new phenomena. In years past, we paddled displacement hull kayaks (rounded on the bottom). This type of hull is rather tippy on a flat surface. Many modern kayaks (and C1's) have planning hulls (basically flat on the bottom). Combine a planning hull with some soft plastic and flat land a boof - presto, your are stuck. You can also get stuck plastered against a side wall of rock and the water current along with lots of friction will hold that boat quite well.
