It was developed by transport engineer Keith W. Tantlinger from Spokane in Washington. The relative obscurity of this invention belies its importance to a more efficient world trade and transport, as the Tantlinger lock made handling and stacking standard containers much easier.
The female part of the connector is the 7×7×41⁄2 in (180×180×110 mm) corner casting fitted to the container itself, and which has no moving parts, only an oval hole in the bottom. The hole is an oval 4.9 in (124.5 mm) on the long axis with two flat sides 2.5 in (63.5 mm) apart. The male component is the twistlock, which is fitted to cranes and transport bases. This can be inserted through the hole (it is roughly 4.1 in or 104.1 mm long and 2.2 in or 55.9 mm wide), and then the top portion (normally pointed to make insertion easier) is rotated 90° so that it cannot be withdrawn. The mechanism is the same as that of a Kensington lock, but on a much larger scale. The maximum size and position of the holes in the connector is defined in international standard ISO 1161:1984.
A major advantage of this approach to attachment is that containers, which may be stored or transported without being inspected for months at a time, do not require any maintenance in order to function effectively. Even with long term exposure to the weather the container remains as simple to move as ever. Only when corrosion is very extensive (to the extent of being easily visible by the mover) does the twistlock become dangerous to move the crate by. The male part is placed on vehicles and equipment that are inspected very frequently and will work with all containers while working effectively.