How do I use a compass on Dartmoor?

I've been busy with the camera and my worn out map to hopefully give newcomers to Letterboxing some idea on how to use a compass with your map. This tutorial will help you plot most of your clues onto your map before going out on your search.
Firstly when using a map get yourself a good detailed one. The one I use that shows just about every detail is Ordnance Survey 1:25 000 Outdoor Leisure Map
How to read the grid references on the map.
Ok, Along the sides, top and bottom you will find grid number. Say with the grid reference of 73 77, the first number 73 you will read along the top or bottom of the map. The number 77 would be read along the left or right hand sides of the map. So think vertical first, then horizontal. Try this grid reference out and you should end up at Bonehill Down.
You can also use a six grid reference number say 731 775 this will give you a much more accurate bearing. The 1 & 5 added would mean that grid 73 77 is split into 10 blocks up and 10 blocks across, so the 1 would be 1 block across and the 5 would be 5 blocks up in the grid.If this sounds confusing you will get some idea from my photo below.
Some people use even more accurate grid references and can be up to 10 numbers! Click on Image 1
Image 1 Image 2 Image 3 Image 4
Picture 1 Picture 2 Picture 3 Picture 4