"If you choose to do this it might be good to do it with an eraseable pencil, otherwise you'll end up with either a lot of lines on your map or an inaccurate declination over time. Magnetic declination is not static. It changes from year to year."

True that magnetic deviation is not static but I wear out a map long before there's a need to change any magnetic north gridlines. :)

All: I should have pointed out that we like compasses with built-in declination, as all Canadian topo maps are printed with a 1000 Metre Universal Transverse Mercator Grid, and a handy arc showing how far off this is from Magnetic North, and True North.

So, no pencil lines in Canada! Use the UTM grid! Mind you, the place was only completely mapped in the mid 1980's, and many of our 'maps' North of 60 are 'photo maps', meaning top-line versions of aerial photos from the 1940's!As well, nothing more detailled than 1:50,000 for the Can. national topo system (a few mine areas=1:25,000!)---I envy European and orienteering maps at 1:10,000!

Always having UTM grid available on a map means pretty much always using the Silva 1,2,3 system to get around.

You do need to note which UTM Zone you are in, as the UTM grid numbers do repeat---we use Lat. + Long. for setting up stuff with aviators...

I used the Suunto today for an insurance bearing when coming down from above treeline via a braided horse-foot-ATV series of trails, worked like a charm. Didn't even have to stop walking!