How do.. Mainly sounds ok, be carefull with the auger thou cos it will give you a dead leg or two. usually 2 foot in the ground is fine unless it s in a windy site and you need to go deeper, the deeper the better thou. The rails sound undersize, you really need either arris rails 75x50 ish or i prefer 100x38 mm rails, they last longer and are better to fix to. they r normaly 2.4 m long or 4.8 and span two bays. the gravel boards need to be the same length. Getting the levels right is not too bad, set your string line 150 mm above ground level, if more than 20 m long put in more stakes on the fence line, pull the line as tight as it will go.. mark out post centres by laying out rails and marking positions, dig holes, if the fence is featheredge and the rails are nailed on the posts you will need a block to attatch the gravel board onto( 150 mm long peice of a rail, needs to be the same thickness). cut as many as you need for 1 per post, use 1 of feather edge boards, lay it on the post flush with the top and nail the block flush with the bottom of the board, this sets the height of your fence so your posts and boards are the same level.
Put in the first post, adjust hole so the string line is just on the top of the block ( dig deeper if necc ) line touching post,concrete in ,semi dry mix, ram in stages getting it upright. nail on 150x20mm gravel board to first post on the block flush with top of block. check next hole and if ok then fix gravel board in centre of 2nd post and your away. when there all in leave for a few days and nail on rails, 100 mm from top and bottom of post, 6' fence needs 3 rails, nail on boards with 2" nails . 4" for rails
Hope this has been usefull
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