How did Travis mark the pigs born that year in Old Yeller?
Travis undertakes the dangerous job of marking the pigs born that year by climbing a tall tree with a strong branch the sticks out to the side. Old Yeller then herds the pigs under the branch, where they stand at bay, facing outward, forming a circle with the young pigs in the middle. Whenever one of the young pigs happens to trot under the branch on which he is perched, Travis drops a lasso down, catching the pig in the rope's loop and hauling him up into the tree. There, Travis grabs him, and quickly and efficiently executes the messy work of marking and castrating the pig.
Travis marks the pigs by cutting into their ears in a distinctive manner. Each settler has a mark which is recognized by all the others, identifying the owner of the pig. The Coates' mark is "overbit the right and underslope the left". To make the family's mark on the pigs, Travis takes the right ear of the animal, folds it, and slices out "a three-cornered gap in the top side, a mark that (is) called an overbit". He then takes the left ear, and on the underside slashes off "a long strip that run(s) clear to the point...an underslope". All the settlers know the hog mark of everybody else and all repect them...they would never butcher or sell a hog that did not belong to them (Chapter 9).