Fences and Gates - fence post

Hi

I am going to attempt to build a fence 16 feet long and i
want to know how to know how and when the 2 post are aligned. i read about a string but hate to sound stupid but
i understand the first post install but the next one 8ft apart
i understand to put a string from the first to the second but
how does that tell you if they are align especialy in the middle of a lawn i am just confuse can someone explain in more lamans term ,thanks

Toby

In 16' of fence with 8' sections you will have 3 posts. Set the 2 end posts where you want them and then pull a string between them to line up the center post.

You will need three posts. What you do is decide where you want your fence line. Take two stakes and place them in the ground a couple feet behind where your two end posts will go. Tie a string to each stake and that will be your fence line. Dig and set your two corner posts first, using that string as a reference. After you set your corner posts, tie a string about a foot up connecting each post. That will give you a reference to place your line post. The reason you want to keep your sections at 8' centers or just under; is because standard 2x4 rails come in 8' lengths. If its over 8' centers you will have to use a 10' 2x4 and cut it. It will cost you a little more money and its a waste.