Joining and assembly

A plain butt joint (two glued square edges) is weak -- small gluing area, no mechanical interlock. To strengthen it, name a specific fix: a corner block, a KD block fitting, dowels across the joint, or pins/screws and glue. Each adds gluing area and a mechanical link so the joint resists twisting. "More glue" does not address the weakness and scores nothing.

Hinge questions want the correct named hinge, not a default butt hinge. A butt or back-flap hinge suits a small door, flap or stand; a tee (T) hinge suits a wide, heavy gate whose strap spreads the load; a piano (continuous) hinge runs a lid's full length so a long edge won't sag. Writing "butt hinge" where a tee or piano is needed loses the mark -- name it and give the reason.

Asked why a dowel joint beats a plain butt joint, candidates often only repeat that it is stronger. Give the reason: the dowels add a larger gluing area and a greater cross-section across the joint, and they stop it twisting, so it resists pulling apart. Naming the mechanism -- more glue area, greater diameter, less twisting -- earns the mark, not the conclusion.

Contact adhesive is described wrongly when candidates try to clamp it. It is spread on both faces, left until touch-dry (tacky), then the surfaces are pressed together and bond on contact -- so it needs no clamping and must be positioned right first time, because it grabs immediately. Clamping while it dries describes PVA or resin wood glue, not contact adhesive.

Temporary vs permanent describes whether a joint can be undone without damage, not how strong it is. A nut and bolt is temporary yet can make a very strong, load-bearing joint -- it is temporary because it can be unbolted. A KD fitting holds a flat-pack cabinet firmly yet lets it be dismantled. Choose by product need, not by assuming permanent = strong.

Both are permanent joints in sheet metal, but they differ by access. An ordinary rivet needs both sides -- the far tail is hammered over to form a head. A pop (blind) rivet is set from one side only with a rivet gun: the mandrel pulls up a head on the far side and snaps off, needing no rear access. An ordinary rivet where only one side is reachable loses the mark.

A trap: thinking welding is a hotter soldering where a filler melts and glues two unchanged parts. In soldering and brazing the parent metal is NOT melted -- only a lower-melting filler (tin solder or brass spelter) melts and holds the parts. In welding the parent metals themselves melt and fuse into one piece. That is why a weld is strongest: no join line of a weaker metal.