The two pictures above show two sides of the same bridleway signpost on the South Downs Way. The arrows both point east and there is a clue to this in the photos. It is not in the lichen growth, which unusually is quite similar on both sides, but in the colour of the arrows themselves. The blue of the south-facing (but east-pointing!) arrow has been bleached more by the sun. The three main weathering clues are sun, wind and rain. The first will usually be greatest on the southern side, but wind and rain will usually leave their marks more prominently on the southwestern side.