In engineering, and shim is a thin and often tapered or wedged piece of material, used to fill small gaps or spaces between objects. Shims are typically used in order to support, adjust for better fit, or provide a level surface. Shims may also be used as spacers to fill gaps between parts subject to wear.

Many materials make suitable shim stock, or base material, depending on the context: wood, stone, plastic, metal or even paper. High quality shim stock can be bought commercially, for example as laminated shims, but shims are often created ad hoc from whatever material is immediately available.

Industry Applications:

• Aerospace engineering
• Automotive engineering
• Carpentry
• Fencing
• Lock picking
• Luthiery
• Masonry
• Motorcycle maintenance
• Nuclear magnetic resonance/Magnetic resonance imaging
• Plumbing
• Tank (vessel) levelling
• Computer hardware