An amentum is a long leather thong that attaches to a javelin.
Benefit: Before throwing, the amentum is wound about the javelin’s shaft. You then throw the javelin while gripping the amentum, imparting spin to the weapon and greatly improving its range. Attaching an amentum to a javelin is a move action, and winding it is a full-round action. Javelins can be stored with amenta already wound about them. A javelin wound with an amentum is considered a martial weapon.