Frame particularly for stretching a piece of painting canvas

A frame particularly for stretching a piece of painting canvas laid thereon, which comprises four wooden strips or strips of an equivalent material arranged to form a quadrangle, the converging strips at each corner being jointed together by jointing in a right angle type of joint, said joint having a box-like structure provided with two converging channels or spaces, each receiving a strip longitudinally insertable thereinto with its end portion, wherein each strip has a prismatic configuration of generally rectangular cross-section, a step formed along the major surface thereof, thus defining a peripheral face which projects further out and whereon the piece of canvas can rest, and an underlying recessed face, underneath the canvas piece, and out of contact therewith when the canvas piece is stretched, each strip having at its end portions a 45.degree. beveled end provided with a through slot extending longitudinally and parallel to the cross-section minor side of the strip and separating, at said step, the end of the strip into a rib portion and a tongue portion, each having a rectangular cross-section, and wherein, according to the inprovement the joint is composed of a laminar material and comprises a flat base defining two converging and communicating channels at a right angle to each other, into which channels there are insertable and guidable, respectively, the tongue portions of the strips with the outer side wall of each channel inserted within said slot, said rib portion resting on and being guided by a portion of the base plane of the joint projecting beyond the channels, at the outer apex formed by the two channels a ridge perpendicular to the base plane in a diagonal direction externally to the box structure formed by the two channels, at the inner apex of the two channels convergency portion a window and an adjusting element insertable through said window.