Cavity and solid walls. 1  A cavity wall is made up of two walls with a gap in between, known as the cavity; the outer leaf is usually made of brick, and the inner layer of brick or concrete block.  A solid wall has no cavity; each wall is a single solid wall, usually made of brick or stone.
A cladogram (from Greek clados branch and gramma character) is a diagram used in cladistics which shows relations among organisms.
A parallelogram is a quadrilateral with 2 pairs of parallel sides. Enjoy a range of free pictures featuring polygons and polyhedrons of all shapes and sizes, including simple 2D shapes, 3D images, stars and curves before heading over to our geometry facts section to learn all about them.