For AWI, where I use snakefencing which in real life is 6 feet high and made of thick logs, I give them a morale save, otherwise for normal fences I don't - they just give a move penalty usually.
Thing is, fencing isn't really obscuring in the ways the rules describe that modifer, so I think the morale modifier is right.
Surely it depends on the Period and the type of fence.
An open rail fence isn't going to be much in the way of cover against a Martini-Henry but a solid fence might give some protection against an early musket?
In the ACW fences were often more of a benefit to the shooter to lean a weapon on to take better aim rather than as a defensive benefit.
This is something for a rule made up to suit your own game period and interpretation of history
I reckon they might obscure enough to make it more difficult to hit, but not to save against. So I would give the -1 to hit, but not the +1 to the morale save. Also remember that the fence would remove the charge bonus of +1 to hit.
'Course if you've got bits of shrubbery (then place it here beside this shrubbery, only slightly higher) and whatnot growing around the fence you've got some cover from that too.
"You're a big man, but you're in bad shape. With me, it's a full time job." – Lt. Bromhead to Prince Dabulamanzi before the Battle of Rorke's Drift.
The rule book (QRS under morale) mentions both light cover and heavy cover. Light cover is "hedgerows or similar". Is a fence similar? I was at Gettysburg this summer and the ranger said they counted 800 musket balls in one one rail of a rail fence at the angle. Was that cover?
What about fences and stone walls causing a target not to be clear? If not clear then it's a +1 to hit. If its light cover then it's also a +1 morale save. So that would be 5+ to hit and 3+ to save with a 4 morale stat.
Also if fences and stone walls cause a target to be unclear (not as visible) what do you guys play as far as definable position? Directly touching the obstacle? Within one base width? Or just define these details at the start of the game and agree on them? The rulebook is somewhat loose (or flexible) on these things.
I think that it is open to interpretation. So, at the beginning of your game, discuss fences with your opponent and agree on what they constitute. Job done