Boundary Chalk

https://www.d20pfsrd.com/magic-items/wondrous-items/a-b/boundary-chalk

Aura moderate evocation; CL 10th; Weight —; Slot none; Price 10,000 gp

DESCRIPTION

The surface of this stick of white chalk is covered with silvery runes.

Drawing a line with the chalk creates a wall of force that is as long as the line and extends 10 feet perpendicular to the surface on which the line was drawn. Drawing a 5-foot line is a standard action that provokes acts of opportunity. Each wall lasts 10 minutes; the bearer of the chalk can dismiss a section of wall as a swift action by touching the stick of chalk to it. One stick of boundary chalk can draw 100 feet of line before it is used up, and it must be used in 5-foot increments.