An anti-grav sled, sometimes referred to simply as an anti-grav, was a device used to carry objects which were too heavy to lift manually. The technology used was similar to a hovercraft or anti-grav lift.
The flow capacitor was one component of an anti-grav sled; however, Reginald Barclay accidentally referred to it as a "flux capacitor" while recounting an embarrassing incident to Deanna Troi. She either did not notice the mistake, or did not want to correct the lieutenant, who had already been corrected by the seventeen-year-old Wesley Crusher earlier. (TNG: "Hollow Pursuits")
Kasidy Yates and her crew sometimes used anti-grav sleds to transport cargo into her cargo ship. Although Benjamin Sisko suggested using the transporter instead, her transporter was a Mk. V, which was ill-equipped to transport unstable bio-matter. (DS9: "Family Business")