A corbel in architecture is a protruding bracket used as a support. In other words, a form of shelf bracket, usually with a curved piece spanning the two legs. Some are quite ornamental, but these are a simple mixture of rectangluar solids and an arc.
These brackets could be useful for building small shelf units such as spice racks, for modelling buildings (dollhouses, model railroads, etc.), or pretty much anywhere else you need a small support.
The OpenSCAD file is fully parametric, so many sizes and variations can be created, as shown in the photo.
OpenSCAD parameters below, most are self-explanatory. Some trial and error might be needed to get exactly the arc you want. Note the arc is always circular but can be moved in and out and up and down as desired. This is usually necessary when the length and depth are different.
length = 50; //overall length of bracket
depth = 50; //overall depth of bracket
widthOuter = 12; //overall width of bracket
widthInner = 10; //width of inner board
thicknessOuter = 4; //thickness of outer board
thicknessInner = 3; //thickness of inner board
innerOffsetX = 1.5; //how much the inner board is offset in the x dir
innerOffsetY = 1.5; //how much the inner board is offset in the y dir
thicknessArc = 5; //thickness of inner arc support
arcInset = .5; //inset the arc equally on each side of inner bioard
arcOffsetX = 4.5; //move the arc inwards in relation to the bracket
arcOffsetY = 4.5; //move the arc in relation to the bracket
arcLenX = -3; //adjust length of arc in X
arcLenY = -3; //adjust length of arc in Y
arcAngle = 5; //how round the arc is, smaller=rounder
I have uploaded several different parameter sets in OpenSCAD for anyone who wants to see how a particular version was set up.