Flatline Guitars is a small, handmade electric guitar maker founded by Rick Lockhart, who builds instruments alongside his father, Rick Sr. The shop began in Aberdeen, Washington and later operated out of Brooklyn, New York, producing guitars in low volumes with each instrument hand-built and set up in-house.

The lineup centers on vintage-inspired solidbody designs. Notable models include the Biscayne, a Jazzmaster-leaning guitar offered with humbucker or P-90 pickups; the Vistaglide Standard and Vistaglide Custom, mahogany-bodied P-90 instruments aimed at jazz and classic rock tones; and the Delta T and Delta 90, Telecaster-style guitars with single-coil or P-90 configurations. Standard appointments across the range include Kluson tuners, string-through-body construction, and vintage-style finishes, and left-handed versions of any model are offered at no upcharge.

Flatline has 2 products cataloged on Equipboard, including Solid Body Electric Guitars. Their gear is featured by 2 artists, with the strongest followings in Rock, Pop, and Folk, World, & Country. Notable users include Phil Keaggy and Scott Tournet.