The most difficult task in building a fence is digging the holes for the posts. This can be backbreaking labor. A typical post will be 4 feet by 4 feet and 8 feet high. At least 1/3 of post should be underground. The hole should be twice the diameter of the post, which requires digging a hole 2 feet deep and 1 foot around. This is no easy task, but there are few things to do that will make the job easier and faster.
Avoid digging in hard rocky soil and sandy soil. Hard rocky soil is just difficult to move, and sandy soil will keep refilling the hole as you try to dig it. If the purpose is to dig post holes quickly and easily the soil makes all the difference.