You will get a lot of strange looks, as most muggles just walk past, not looking at their surroundings.
You need to do some counting. If you are by yourself, I would get prepared to take your shoes off. (the numbers are that large!)
OK enough frivolous chatting, lets get down to it:
There are four areas: where you are standing, the tunnel for the muggles, north wall from the tunnel, and south wall from the tunnel
The cache is hidden at:
South 37 degrees (the number of bolts on the south wall minus the number of bolts in the garden).(the number of screwdrivers in the tunnel minus the number of spanners on the north wall)(the number of bolts sticking straight up at either end of the tunnel)(the number of pliers in the tunnel)
East 144 degrees (the number of screwdrivers on the south wall)(the number of spanners on the south wall).(the number of Phillips head bolts in total)(the number of pliers on the north wall)(the number of nuts looking for the cache)
Remember: if it's not made of concrete, it's not worth counting.