What is a Door Shim?

A door shim is a thin, flexible locksmith tool used to bypass certain spring latch locks without a key, by slipping between the door and the frame and manipulating the latch bolt directly. Door shims — sometimes called latch shims or lock shims — are commonly made of thin metal or durable plastic and are a staple in every locksmith's non-destructive entry toolkit, especially for residential lockouts.

How to Shim a Door

To shim a door, a locksmith inserts the shim into the gap between the door and the door frame, positioned near the latch bolt rather than the deadbolt. The shim is angled and slid downward or upward along the frame until it makes contact with the beveled edge of the spring latch. Light pressure is then applied to push the latch back into the door, allowing the door to be opened without turning a key or damaging the lock.

How Does a Door Shim Work

A door shim works by exploiting the beveled shape of a spring latch bolt. Because the latch is angled to allow the door to close and catch automatically, that same angle can be pushed back with steady pressure from a thin, rigid shim. As the shim slides along the strike plate and contacts the beveled face of the latch, it forces the latch bolt to retract into the door, releasing it from the strike plate so the door swings open freely.

How Many Shims Per Door

Most residential doors with a standard spring latch only require a single door shim to bypass the lock. However, locksmiths often carry two shims for doors with double doors or French doors, where the latch or an astragal strip may need to be manipulated from both sides simultaneously. Doors with deadbolts engaged, or high-security spring latches with anti-shim guards, cannot be opened with a shim alone and require different entry tools.

When Locksmiths Use a Door Shim

Locksmiths reach for a door shim in situations such as:

• Residential lockouts where only the spring latch is engaged (not the deadbolt)

• Interior doors, closets, and cabinets with simple latch locks

• Emergency entry calls where speed and minimal damage are priorities

• Situations where drilling or force would damage the door or frame unnecessarily

Door shims are best suited for quick, low-risk lockout calls rather than high-security or deadbolt-engaged doors.

Types of Door Shims

Door shims come in a few common types, each suited to a different scenario:

• Metal shims — thin, rigid strips of steel or spring steel, durable and reusable for repeated professional use

• Plastic shims — flexible, low-cost shims often used for lighter-duty or occasional lockout work

• Credit card-style shims — flat, card-shaped shims designed to mimic the classic "credit card bypass" technique with more durability and control

• Double-sided shims — designed for French doors or double-door setups where two latches must be manipulated together

Limitations of a Door Shim

Door shims have clear limitations locksmiths and customers should understand:

• They only work on spring latch locks, not deadbolts or high-security cylinders

• Many modern locks include anti-shim latches with a secondary plunger to block this method

• They are not effective on doors with multiple locking points or reinforced strike plates

• Improper technique can scratch paint, damage weatherstripping, or mar the door frame

Advantages of Using a Door Shim

Despite their limitations, door shims remain a valuable tool for the right job:

• Fast, non-destructive entry that avoids drilling or lock replacement

• Low cost and lightweight, easy to carry on every service call

• No damage to the lock itself, preserving the customer's existing hardware

• Simple to use with minimal training, making it a reliable first option for eligible lockouts