Oakum
Oakum is a preparation of tarred fibre used to seal gaps. Its main traditional applications were in shipbuilding, for caulking or packing the joints of timbers in wooden vessels and the deck planking of iron and steel ships; in plumbing, for sealing joints in cast iron pipe; and in log cabins for chinking. In ship caulking, it was forced between the seams using a hammer and a caulking iron, then sealed into place with hot pitch.
Saltine cracker
Flat saltine crackers have perforations on their surfaces. During baking, the outer layer of dough hardens first, restricting out-gassing of evolved gasses. The perforations connect the top surface to the bottom surface to prevent the cracker from pillowing as a result of these evolved gasses.