These macromolecules are polar [polar: having different ends] because they are formed by head to tail condensation of polar monomers. Let's look at the three major classes of macromolecules to see how this works, and let's begin with carbohydrates.
Bostwick Steel Lath Company advertisement for steel truss loop type metal lath in 1920. A lath or slat is a thin, narrow strip of straight-grained wood used under roof shingles or tiles, on lath and plaster walls and ceilings to hold plaster, and in lattice and trellis work.
Plaster and lath refers to an older style of interior wall that uses wooden lath attached directly to the studs; the lath is then embedded with plaster. The plaster dries to form a hard, smooth surface suitable for finishing with paint or wallpaper. Plaster and lath is rarely used now, except to repair existing plaster and lath walls.