placeFence

local size = 64

local index = 1
turtle.select(1)
local function place()
  while turtle.detectUp() do
    turtle.digUp()
  end
  turtle.digDown()
  turtle.placeDown()
  if turtle.getItemCount(index) == 0 then
    index = index + 1
    if index > 16 then index = 1 end
    turtle.select(index)
  end
end

place()
for i = 1, 4 do
  for j = 1, size-1 do
    while turtle.detect() do
      turtle.dig()
    end
    turtle.forward()
    place()
  end
  turtle.turnRight() -- Goes clockwise
end