Invulnerable Field (3.5e Spell)

''With a long string of words, you bind an object to some area. The object begins to glow with a shifting light, and a faint force field appears around the area, preventing entry or exit.''

When you cast this spell, choose an object within close range that has combined hardness and hit points no greater than five times your caster level. Until that object is destroyed, the affected area loses line of sight to it, the affected area loses line of effect to it, or it comes within 10' of the area, the area cannot be entered or exited. While impervious to entry or exit, it is impossible for anything to cross the boundary, and teleportation or planar travel into or out of the area is impossible as well.

If the area regains line of sight and line of effect to the object, and the object is once again more than 10' away from the area, the area returns to its unenterable, unexitable state.

A Spellcraft check to identify this spell also identifies which object is sustaining it.