More and more modern combines come with built-in side-knives, meaning there are increasing numbers of bolt-on units lying in the corner of farm workshops and occasionally popping up on eBay.

That means it’s now more affordable than ever to have the ultimate luxury that any self-respecting combine driver dreams of – side-knives either side.

With one on the left and another on the right, it’s no longer compulsory to cut in lands and striking out through the middle of a crop is pure pleasure.

But getting them installed correctly is pretty important, particularly if the electrical jiggery-pokery of your prized new find looks a little dubious.

We got hold of wiring kits from spare-parts supplier Spaldings and the importer of Matrot side-knives, Garford, and set about fitting them.

See also: 16 nifty retrofit items to fine-tune your combine

Watch the video to see how to fit them and read the report below.

Switches

The Spaldings box is pretty much ready to go once power-in and power-out cables are connected. The Garford kit will require a hole drilled in the control console to accommodate the 70s-style chrome throw-switch.

For a less permanent fixture we commandeered an old control box. From there, run the supply back out to under the cab.

Making the connection

The wiring kits suggest using the supplied quick-couplers to connect up with the side-knives down at the point where the mounting brackets are bolted to the header.

Instead we opted to have the connections up under the cab on the same side as the hydraulic couplings. That way, nothing can get forgotten and everything is in one place.

Cabling needs to be routed carefully to avoid clashes with the reel and zip-tied where it’s likely to snake out and snag on fence-posts and gate hinges.

Wiring kit verdict

Spaldings

The Spaldings kit is heavy-duty, but at more than £250, it’s pricey too. That said, it’s got a ready-wired control box with in-built overload protection.

But being pre-assembled doesn’t really make it any more straightforward to install – the lengths of cable from battery to cab and back out again to the header will inevitably need chopping about – it’s not one size fits all.

Garfod

For a fifth of the price, the Garford kit is understandably more sparse, with just a single run of cable, some quick-connectors, a simple switch and a 50-amp fuse as overload protection.

While the Spaldings set-up is the most easily transferrable between machines, the Garford is a more permanent fixture.