1)          If a particular casting of a knock spell has the power to affect the portal in question (i.e. two or less methods of preventing egress), then the portal does actually physically open under the power of the spell. This doesn’t mean that the door or chest that the spell was cast upon flies open violently, unless there is pressure behind the portal already (eg. from a spring loaded trap behind the portal). Rather, a door would open a few inches, a chest lid might pop up a millimetre or two, or riveted shackles might pop open enough to slip the adjacent link off, after the methods of preventing egress have been passed.

2)          The spell bypasses the “weakest” methods of preventing aggress first (eg. a stuck, barred, locked and wizard locked door would become unstuck first, have the bar lifted next, the lock opened next and the wizard lock bypassed last of all.

3)          The bypassing of methods of preventing egress through the use of the knock spell does not guarantee that the bypassing has been done silently.

4)          The opening of “welds” or “rivets” on shackles does not imply that other welds or rivets, such as those in a structure or on an item like armour, are affected. These latter rivets are unaffected by a knock spell as these are not “portals” or “openings”.

5)          A single “weld” or “rivet” is counted as one method of preventing egress.


1. Ref: 2nd Edition Player’s Handbook

Description of the 2nd Edition version of the Knock spell

Knock (Alteration) Reversible

Level: 2nd

Range: 60 yards                                                       Components: V

Duration: Special                                                     Casting Time: 1

Area of Effect: 10 sq. ft/level                                Saving Throw: None

The knock spell opens stuck, barred, locked, held, or wizard-locked doors. It opens secret doors, as well as locked or trick-opening boxes or chests. It also loosens welds, shackles, or chains. If used to open a wizard-locked door, the spell does not remove the former spell, but simply suspends its functioning for one turn. In all other cases, it permanently opens locks or welds – although the former could be closed and locked again later. It does not raise barred gates or similar impediments (such as a portcullis), nor does it affect ropes, vines, and the like. Note that the effect is limited by the area;  a 3rd-level wizard can cast a knock spell on a door of 30 square feet or less (for example, a standard 4-ft. x 7-ft. door). Each spell can undo up to two means of preventing egress through a portal. Thus if a door is locked, barred, and held, or triple locked, opening it requires two knock spells. In all cases, the location of the door or item must be known – the spell cannot be used against a wall in hopes of discovering a secret door.

The reverse spell, lock, closes and locks a door or similar closure, provided there is a physical mechanism. It does not create a weld, but it locks physically operated locking mechanisms, set bars, and so on, up to two functions. It cannot affect a portcullis.

2. Ref: Dragon Magazine, February 1991 (Issue 166, pg 72)

Is there a limit to the thickness and strength of the welds or rivets a knock spell can break? Could the spell break a welded link of a massive chain holding up a bridge? Could it pop a rivet out of a battleship?

A knock spell cannot do either of the things you have described. The spell opens closures; it does not destroy structures. If a closure that can be opened by a knock spell (doors, lids; shackles, etc.) is sealed with a weld or rivet, the spell will break the weld or rivet, provided that the closure is not larger than the spells area of effect. For example, a pair of handcuffs riveted shut will pop open when knocked. Note that the spell description (see the Player’s Handbook) does not specifically mention rivets, but these should not be allowed to provide an easy way around knock spells. However, a single rivet is one “means of preventing egress.” A single knock spell pops two rivets sealing an opening.

3. Ref: Dragon Magazine, September 1981 (Issue 53 pg 56-57)

Extract from an article on procedures for opening doors.

A knock spell, as per its description, will negate two forms of securing. Always eliminate the weakest security device first. A knock cannot lift a portcullis, but a levitate spell might be able to do so. A knock can drop a drawbridge only if cast directly at the mechanism that opens and closes the drawbridge. Finally, knock is not silence, and incidental noise can easily arise from numerous causes.