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.
Tyrannosauridae
William Abler observed in 2001 that "Albertosaurus" tooth serrations resemble a crack in the tooth ending in a round void called an ampulla. Tyrannosaurid teeth were used as holdfasts for pulling meat off a body, so when a tyrannosaur would have pulled back on a piece of meat, the tension could cause a purely crack-like serration to spread through the tooth. However, the presence of the ampulla would have distributed these forces over a larger surface area, and lessened the risk of damage to the tooth under strain. The presence of incisions ending in voids has parallels in human engineering. Guitar makers use incisions ending in voids to, as Abler describes, "impart alternating regions of flexibility and rigidity" to the wood they work with. The use of a drill to create an "ampulla" of sorts and prevent the propagation of cracks through material is also used to protect airplane surfaces. Abler demonstrated that a plexiglass bar with incisions called "kerfs" and drilled holes was more than 25% stronger than one with only regularly placed incisions. Unlike tyrannosaurs and other theropods, ancient predators like phytosaurs and "Dimetrodon" had no adaptations to prevent the crack-like serrations of their teeth from spreading when subjected to the forces of feeding.