Cord puller is a diagonal sawtooth that was discovered by Dean Hickerson on May 14, 1991. It has expansion factor 6.
It works by firing pairs of gliders at the back of a 7-engine Cordership so that when the first pair hits the Cordership, a block is created in the path of the following glider pairs. When those pairs hit the block, it is pulled back closer to the gun at the southeast. When the block reaches the gun, it is destroyed, allowing the gliders to reach the Cordership again and start the process over again.
Its population in generation t = 8(6n) - 216 (n ≥ 2) is t/36 + 558, but the population in generation 32(6n) - 429 (n ≥ 2) is only 469.
The number of alive cells plotted versus the number of elapsed generations
roughly forms an ever-increasing sawtooth graph.