Deadeye

The three-holed blocks were called deadeyes because the position of the three holes resemble the eye and nose sockets of a sheep's skull.

[1] Single deadeyes (or bull's eyes) are used to guide and control a line and, particularly in older vessels, to change its direction.

Triple deadeyes are used in pairs; a line called a lanyard is run back and forth between them, through the holes, so that they function again much as a block and tackle would.

A small wooden wedge is knocked into the last hole, to prevent the lanyard sliding back, and the end is unhooked from the purchase and made up on the shroud above the upper deadeye.

[3] Modern deadeyes, also known as chainplate distributors can be made of titanium or aluminum, manufactured by vendors such as Colligo Marine.