Which objects can be placed between piano strings to prepare a piano?

A prepared piano is an instrument that has been modified by placing various objects between its strings to produce unique percussive and otherworldly sound effects.12

Commonly used items for these preparations include nuts and bolts, which are inserted between the strings to alter their vibration and timbre. These modifications allow the instrument to generate a wide range of sounds—such as buzzing, clanging, clunking, thumping, and rattling—while still maintaining the piano's fundamental melodic qualities. This technique is famously associated with the American composer John Cage, who utilized these preparations in works such as Sonatas and Interludes for Prepared Piano.1