Frame support system

An adjustable mechanical assembly comprising:

• a plurality of corner pieces each having:
• a first opening facing a first direction having a first cross-sectional shape;
• a second opening facing a second direction, orthogonal to the first direction having the first cross-sectional shape;
• and
• a cavity connecting the first opening and the second opening,
• wherein the plurality of corner pieces form corners of the adjustable mechanical assembly when assembled with a plurality of edge pieces;
• the plurality of edge pieces having a second cross-sectional shape, different from the first cross-sectional shape, wherein the first cross-sectional shape can be formed by an arrangement of two or more of the edge pieces, a first one of the two or more edge pieces positioned approximately perpendicular to at least a second one of the two or more edge pieces in the arrangement, wherein the edge pieces, when arranged to form the first cross-sectional shape, are inserted into respective openings of the corner pieces to form sides of the adjustable mechanical assembly;
• and
• a protruding member extending from the cavity in a third direction, orthogonal to the first direction and orthogonal to the second direction.