SRD:Heavy Shield

Description
You strap a shield to your forearm and grip it with your hand. A heavy shield is so heavy that you can’t use your shield hand for anything else.

Wooden or Steel: Wooden and steel shields offer the same basic protection, though they respond differently to special attacks.

Shield Bash Attacks: You can bash an opponent with a heavy shield, using it as an off-hand weapon. Used this way, a heavy shield is a martial bludgeoning weapon. For the purpose of penalties on attack rolls, treat a heavy shield as a one-handed weapon. If you use your shield as a weapon, you lose its AC bonus until your next action (usually until the next round). An enhancement bonus on a shield does not improve the effectiveness of a shield bash made with it, but the shield can be made into a magic weapon in its own right.

Enhancements
Shield Spikes: When added to your shield, these spikes turn it into a martial piercing weapon that increases the damage dealt by a shield bash as if the shield were designed for a creature one size category larger than you. Otherwise, attacking with a spiked shield is like making a shield bash attack.

An enhancement bonus on a spiked shield does not improve the effectiveness of a shield bash made with it, but a spiked shield can be made into a magic weapon in its own right.

Compared to a regular heavy shield, a heavy spiked shield costs 10 gp more and is 5 lb. heavier.