Abstract: An all-purpose level in the form of a box that contains a ball rolling on an upwardly concave surface that is a figure of revolution about a vertical axis. The box rests on a member which will be horizontal when the level is in engagement with a truly vertical or horizontal surface. For this purpose, the member is disposed at a right angle to a plate which is hingedly connected to another plate about an axis perpendicular to the plane of the member. The member is selectively lockable in that perpendicular relationship; but when released, the member folds against the first-mentioned plate and the device thus folds about two hinges at right angles to each other, thereby to provide a configuration in which the level can rest on a generally horizontal surface to indicate true horizontal orientation thereof.

Abstract: Briefly stated, the present invention provides a level with a ball rolling on inclined surfaces, the level comprising a window through which the ball can be observed. Reference marks are positioned on the window so as to indicate the horizontal and/or vertical positions of a reference line visible through the window. The level has two spaced transparent lenses or glasses between which the rolling ball is disposed. These can be flat or convex; and if convex, a centrally located reference mark can be provided which indicates the inclination of a surface on which the level rests on its side, that is, with the line of sight through the lenses disposed vertically. This same reference mark, when the lenses are not convex but rather flat, can serve as a target mark for helping to aim the level.