$3.$ Forge welding, one of the oldest welding techniques, involves heating the workpieces to a $\_$ temperature and then applying $\_$ to join them, a method traditionally used by $\_\_\_$ for centuries. $($Options: high, low, moderate, pressure, adhesive, blacksmiths, carpenters$)$

$4.$ Roll welding combines $\_$ and $\_$ to produce a weld along the entire interface of the workpieces, which can be enhanced by introducing a $\_\_\_$ layer to improve bond strength. $($Options: heat, pressure, rotational movement, metallic, non$-$metallic$)$