A property designer or prop designer is a person who designs props

Theatrical property

A theatrical property, commonly referred to as a prop, is an object used on stage by actors to further the plot or story line of a theatrical production. Smaller props are referred to as "hand props". Larger props may also be set decoration, such as a chair or table. The difference between a set...

 for use in theatre, film, television, etc. Prop designers work in liaison with the costume designer

Costume Designer

A costume designer or costume mistress/master is a person whose responsibility is to design costumes for a film or stage production. He or she is considered an important part of the "production team", working alongside the director, scenic and lighting designers as well as the sound designer. The...

s, set designers and sound designers, under the direction of the art director

Art director

The art director is a person who supervise the creative process of a design.The term 'art director' is a blanket title for a variety of similar job functions in advertising, publishing, film and television, the Internet, and video games....

 or technical director

Technical director

The Technical Director or Technical Manager is usually a senior technical person within a software company, film studio, theatrical company or television studio...

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However, the public seems to associate the term with home designer, or an interior designer, a person who is considered a professional in the field of interior design or one who designs interiors as part of their job.