Rawl Drives or Button Heads or Rivets or Split Drives, they are known by several different names but for years they were a climbers drilled anchor of choice. These little spikes of zinc plated steel could inspire confidence when you where clipping them right at face level and could make your legs shake when you stared down at them from some desperate run out scare-fest.
In the formative years of American rock climbing most climbers were putting up routes, drilling by hand, on lead, often from stances with dizzying exposure. Drilling by hand was labor intensive and time consuming so climbers were looking for a good balance between ease of placement and security. 1/4 inch bolt holes were far easier to drill than 3/8 inch studs and climbers could select from a few different depths in the 1/4 inch size (1 1/4 inch to 4 inches at the time these were produced).
Ed Leeper made the most commonly available hangers in the late 1960s. His hangers were relatively thin steel stock but were considered more than adequate for the job at hand. Only later in the late 1970s and early 1980s did climbers discover problems with these thin hangers. Ed stepped up and issued a voluntary recall and warning about cracking at weak points in the design.