An orthodiagonal quadrilateral is a quadrilateral whose diagonals are perpendicular. The midpoints of the sides of any quadrilateral with perpendicular diagonals form a rectangle. A parallelogram with equal diagonals is a rectangle. A Brahmagupta quadrilateral is a cyclic quadrilateral with integer sides, integer diagonals, and integer area. All the letters will appear in both the diagonals, ensuring correct diagonal sum. A golden rhombus is a rhombus whose diagonals are in the golden ratio. Of all convex quadrilaterals with given diagonals, the orthodiagonal quadrilateral has the largest area. In particular, the centroid of a parallelogram is the meeting point of its two diagonals. Horizontal wires were attached to these diagonals. Thus its sides coincide with one side and two particular diagonals of the regular heptagon. These threefold axes lie along the body diagonals of the cube. The two diagonals and the two tangency chords are concurrent. American Navajo Indians used bold diagonals and rectangular motifs. Five-point intersections created by converging diagonals are legion in the older areas. The shapes and diagonals are carefully constructed.