Often there are many natural and man-made obstacles and terrain features on a battlefield that can be used to gain an edge over an opponent. Cover is using features to increase your defensive capabilities while elevation increases your offensive capabilities

Cover Bonuses

Type
Melee (physical damage)
Ranged (physical damage)
Shrubs, Hedge, Fence
none
+5 AC
Trees, Wagons, Barrels
+5 AC
+10 AC
Boulders, Walls
+10 AC
+15 AC
GM discretion in specific situations over rules

Elevation Bonuses

Elevation bonuses are to hit modifiers applied for having an elevation advantage over your target. They typically only apply to ranged hit modifiers unless you possess a weapon or attack with a melee-range indicated. The "Slightly Elevated" option is ana exception and appleis to both melee and ranged hit modifiers. The hit modifier for elevation bonuses is equivalent to +1 to hit per 1/2 inch above the target, up to a maximum of +10 to hit (
Example
Actual height (meters)
Actual Height (feet)
Approx. Model Equivalent
Hit modifier
Slightly elevated (i.e. table)
1m
3'
0.5"
+1 to hit
Half way up a 1 story staircase
2m
6'
1"
+2 to hit
Second story balcony/window
4m
12'
2"
+4 to hit
Battlements on a wooden palisade
6m
18'
3"
+6 to hit
Third story balcony/window
8m
24'
4"
+8 to hit
Large castle wall, flying high overhead
10m or higher
30'
5"
+10 to hit