To elevate or depress the gun a simple wedge or quoin supported on a bed formed by one of the transoms was suitably positioned under the breech, the latter being raised or lowered by a handspike. Although the idea of a screw to apply elevation was conceived at least a century earlier, the first practicable screw did not appear until 1578 (in England). Difficulty of manufacture probably precluded its earlier use, as the screw-cutting lathe had not then been invented. To make a screw, a wooden model had first to be carved, then a mould made in clay, and finally a casting produced. Old-time gunmakers often had the ideas but not the technology to put them into practice. The elevating screw enabled elevation and/or depression to be applied much more accurately than with the quoin, and was in general use in field and siege artillery by 1650. However, the quoin survived until the 19th century, especially in the Navy where battles tended to be short-range affairs, and sailors considered the screw too slow. The double-plate carriage continued in use for nearly 300 years in field artillery and longer in siege.