HIGHER (HALF) JOINTS such as a round pin in a slot (Figure 2-21c) or a carn-follower joint (Figure 2-lOc, p. 41) suffer even more acutely from the slider's lubrication problems, because they typically have two oppositely curved surfaces in line contact, which tend to squeeze any lubricant out of the joint. This type of joint needs to be run in an oil bath for long life. This requires that the assembly be housed in an expensive, oil-tight box with seals on all protruding shafts.