OK.....I had to try this myself. Behind my house the land rises to a hill and at the very top the granite ledge rises out of the ground. I had to put in my own Benchmark. I also had to do it the old fashioned way. By hand. By myself.   I ordered a custom Disk from Berntsen Int'l and tools from doitbest.com. In ordering the disk, I was careful to choose a center design that I do not think is being used by an official agency. Over a 10 day period, I took GPS readings of the location and average