Border Reivers were raiders along the Anglo/Scottish border from the 1200s to the 1700s. Here’s a set of free wargames rules for playing out these skirmishes.
Rules: Medieval
FUBAR Medieval Rules
Following up on their FUBAR modern rules, Gawd ‘elp Us Games offers FUBAR Medievals.
Late Medieval Skirmish Rules
The Late Medieval Skirmish Rules is a set of free wargames rules for large scale figures on an actual dining room table (with salt shakers, etc.)
Sword and Dagger Medieval Skirmish Rules
Sword and Dagger are a set of free wargames rules for medieval skirmishes. They’re very straightforward and at 11 pages, probably good for beer and pretzels games.
Solitaire Song of Blades and Heroes
Dougi has a set of adaptations for solitaire play of the popular commercial set of rules Song of Blades and Heroes.