Bolt-on

Some guitars have the neck glued to the body (Les Pauls), some are bolted on (Fenders), and in some the neck is part of one piece of wood that extends through the body (Jackson). The theory of the neck through the body design is that if the pickups, bridge, and the strings (from tuners to tailpiece) are mounted on the same piece of wood, sustain will be greatly enhanced. In practice, a well joined glue-on and a properly fitted bolt-on will sustain just as well.

Source: wiktionary

I would draw a distinction between transplants and cross-fertilisation. […] Cross-fertilisation implies a different, more indirect process. It implies that an external stimulus promotes an evolution within the receiving legal system. The evolution involves an internal adaptation by the receiving legal system in its own way. The new development is a distinctive but organic product of that system rather than a bolt-on.

Source: wiktionary

Should not a curriculum for the twenty-first century be organised more effectively around the new technology? At present, it remains an addition to most subjects – a bolt-on.

Source: wiktionary

Friday night's crowning victory at The Hawthorns was the 25th in 30 league matches since Antonio Conte's decisive re-gearing of his team in September, the tactical switches that have coaxed such a thrilling run from this team of bolt-ons and upcycled squad players, most notably Victor Moses, who was dredged out of the laundry bin in the autumn to become a key part of the title surge.

Source: wiktionary