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.
Brazing, or soldering, involves a filler metal or alloy (a combination of metals) which has a lower melting point than the metal pieces to be joined. The filler materials (such as lead and cadmium) can be very toxic. Metal cutting is done by heating the metal with a flame and directing a stream of pure oxygen along the line to be cut.