An apparatus comprising a height-adjustable foot of a piece of furniture and the like and a tool for adjusting the height-adjustable foot, wherein the height-adjustable foot having a controlled element which extends into a stem, at least partly threaded (in 11), suitable for being inserted, screwable and unscrewable, into a cylindrical body or another appropriate shape, internally threaded, which can be coupled with a piece of furniture and the like, the tool for controlling said controlled element of the height-adjustable foot in turn comprising: an engagement or control means and a handle for rotating said engagement or control means, said handle comprising two arms suitable for embracing a diameter of said height-adjustable foot to keep the tool and the engagement or control means associated laterally with the adjustable foot, said engagement or control means being arranged between said two arms to face each other and become engaged with said controlled element for rotating said controlled element of said height-adjustable foot, characterized in that said controlled element of said adjustable foot comprises two superimposed toothings (17, 18) formed peripherally on said controlled element and whose teeth are those of saw-toothed wheels tilted in an opposite direction with respect to each other and said engagement or control means comprises a toothing consisting of a toothed section which extends distributed over a rounded area of the surface between said two arms of said handle for engaging with one toothing of the two superimposed toothings (17, 18) formed peripherally on said controlled element of said height-adjustable foot, wherein the teeth of said toothed section and the teeth of said two superimposed toothings (17, 18) of said controlled element are asymmetrical and angled, enveloping, curved teeth that follow a circular trend of said controlled element around the height-adjustable foot. an engagement or control means and a handle for rotating said engagement or control means, said handle comprising two arms suitable for embracing a diameter of said height-adjustable foot to keep the tool and the engagement or control means associated laterally with the adjustable foot, said engagement or control means being arranged between said two arms to face each other and become engaged with said controlled element for rotating said controlled element of said height-adjustable foot, characterized in that said controlled element of said adjustable foot comprises two superimposed toothings (17, 18) formed peripherally on said controlled element and whose teeth are those of saw-toothed wheels tilted in an opposite direction with respect to each other and said engagement or control means comprises a toothing consisting of a toothed section which extends distributed over a rounded area of the surface between said two arms of said handle for engaging with one toothing of the two superimposed toothings (17, 18) formed peripherally on said controlled element of said height-adjustable foot, wherein the teeth of said toothed section and the teeth of said two superimposed toothings (17, 18) of said controlled element are asymmetrical and angled, enveloping, curved teeth that follow a circular trend of said controlled element around the height-adjustable foot.