What are they?
They’re one of the most essential pieces of hardware on any sailboat. Lines run through blocks to create purchase systems or change the direction of the rigging or line. Take a look at some here.
Block and traveler maintenance isn’t something that springs to mind as the most exciting of projects, and for many of us this may be something that gets put to the bottom of the to do list. According to this article by Harken, it really shouldn’t be.