From the workshops the various pieces or parts go to the yard where the slip is on which the vessel is being built. This slip is by the water's edge, conveniently placed with a view to the fact that later on the great structure, weighing possibly thousands of tons, has got to slide down into the water.
Where the keel of the ship is to go a row of timber blocks is placed a few feet apart, and upon these blocks the plates of steel which form the lowest part of the ship are laid. Upon them are laid other parts, and upon them others, the joints being made by riveting. Thus the great ship grows from the keel upwards. As she gets bigger and bigger there comes the danger of her tipping over, and that is provided against by the use of props or shores along both sides.
By the time the hull is ready for launching it is often of great weight, all of which is borne upon the wooden blocks underneath the keel. Consequently, if the ground be not good, piles have to be driven in or concrete foundations laid to enable the huge mass of the ship to be supported. For this reason a large vessel cannot be built anywhere but only on a properly prepared "slip," and it is the possession of a large number of such places which enables Great Britain to build so many ships at once.
Along each side of the slip there is usually a row of tall masts with a beam projecting out sideways near the top of each, forming cranes by which the heavier parts can be hoisted into position.
In other yards, again, there is a tall iron structure called a gantry along each side of the slip, while travelling cranes span across from one to the other
over where the growing ship lies. These travelling cranes, worked by electricity, permit heavy weights to be handled with ease and safety. Other subsidiary cranes, meanwhile, carry the heavy hydraulic riveting machines by which riveting is done.
Much riveting is done by hand, men working together in squads of four. Of these one, often quite a boy, heats the rivets in a small furnace, after which he throws them one by one to man number two, who inserts each as he receives it in its proper hole and holds it there with a big heavy hammer or else a tool called a "dolly." Number two is called the "holder-up," since he holds the rivet up in its place while the remaining two hammer it over with alternate blows of their hammers.
In many cases, however, the two last described men give place to one, who is armed with a tool in shape much like a pistol and operated by compressed air obtained through a flexible tube. When he presses a trigger a little hammer inside the "pistol" gives a rapid series of blows to the rivet, completing the job more quickly than the two men can do with hand hammers.
A third way of doing this operation so important in the building of a ship is by the hydraulic machine suspended from the cranes. To the casual onlooker this has the notable feature of being silent, whereas riveting by hand and still more by a pistol hammer is terribly noisy. The reason for this is that the hydraulic riveter does not hammer at all, but, like a huge mechanical hand, it takes the rivet between finger and thumb and just squeezes it down.