Shields are a staple element of any fantasy game, and a fighter's best friend in combat (besides their weapon, of course). This covers the basic information you need to know to make a shield for use at Knight Realms.
Maximum shield sizes are as follows:
Small - 18" diameter, or 18" height and width.
Medium - 30" diameter, or 36" height and 28" width.
Large - 42" diameter, or 54" height and 36" width.
A shield should be safe - for the person using it, her opponent, and any other items involved in the melee (specifically, boffer & latex weapons that will be hitting it. No one wants to wreck a $100 latex sword on a poorly made shield).
Shields may be made of any material the builder desires, as long as the edges are protected and padded on all sides by 5/8" pipe foam (the same kind used on boffer weapons). Plywood and cardboard have been used successfully in the past, and if treated properly, are durable in even the worst conditions.
A shield should be under the control of its bearer at all times, and should not fly loose in combat. A garage door handle and a strap system on the back will do this nicely, allowing for fine control while allowing for ease of use.
Decoration of a shield is highly encouraged, for both RP and atmosphere purposes - your shield should be easily recognizable from across the battlefield. Please refrain from using symbols that are OOG or modern in nature, as this breaks the atmosphere of the game.