turtle_column_gravel

local slot = 1
local stack = 0
local fail = 0
turtle.select(slot)
stack = turtle.getItemCount(slot)
while turtle.getItemCount( slot ) > 0 do
    if not turtle.placeDown() then
        fail = fail + 1
        if fail > 4 then
            print("Abort")
            return
        end
    else
        stack = stack - 1
        while stack <= 0 do
            slot = slot + 1
            if slot > 16 then
                print("Empty")
                return
            end
            stack = turtle.getItemCount(slot)
        end
        turtle.select(slot)
    end
    sleep(0.3)
end
print("Done")