The Posted Co-ords will take you to the Bridge. You will need to collect some information from the Bridge itself and do some simple sums which will help you obtain the correct co-ords to find the cache.
# The number of floor panels will give you A.
# The number of wooden uprights will give you B.
# The number of wooden horizontals x2 will give you C.
By now you should have all the info that you need!
Checksum - A+B+C+D = 17
The cache can be found at: N 50 59.(A-B)(A-B)(B) W 003 13.(C-B)(A-B)+1)(C/B)
You will need tweezers for the scroll.
The cache is a fair distance from the Bridge but is walkable, you may wish to drive to GZ.
The Little Bridges series was started by Stanthews in 2009 to highlight small footbridges in remote parts of Wiltshire. Since then the series has been expanded by others all over the country and starting to spread fast. There is a stats listing run by Billiethecat, so you can see how many Little Bridges you have found, you can find it here:- https://littlebridgesseries.wordpress.com/ . If you would like to add to the series, please contact Stan on stanthews@aol.com and he will give you a number for your bridge, to qualify, the bridge must be a foot bridge too small for vehicles, please make sure your title exactly matches “Little Bridges # xxxx then the name” including spaces so it will get picked up and added to stats list.