Quick answer
A trailer light board is a single bar carrying all the rear lights you need to tow legally: tail lights, brake lights, indicators, a rear fog, a number plate light and red reflectors. It is a quick, low-cost way to make a small trailer road-legal. It is perfectly legal to use, as long as the lamps end up in the correct positions for the width and length of your trailer. Boards suit small builders’ and box trailers; wider or longer trailers are usually better with permanently fitted lights so the indicators and markers sit where the law requires.
| Feature | What to look for |
|---|---|
| Connector | 7-pin (12N) for lights only, or 13-pin to match a newer car |
| Width | Indicators and markers must sit near the outer edges of the trailer |
| Reflectors | Red triangular reflectors at the rear are a legal must |
| Lamp type | LED for brightness, longer life and far better reliability |
If you have ever borrowed a mate’s trailer and found the lights did not match your car, you already know the appeal of a light board. It bolts or straps to the back, plugs into your towball socket, and turns almost anything into a road-legal trailer in a couple of minutes. They are honest, useful bits of kit, but there are a few things worth knowing before you buy, especially around size and whether to go LED.
What a light board has to do
Whatever you tow, the rear of the trailer must show the right lights in the right places. A good board gives you tail lights, brake lights, left and right indicators, a rear fog light, a number plate light and red reflectors. The reflectors matter: red triangular reflectors at the rear are specifically required on trailers, and a quality board builds them in. For the full legal picture, see our guide to trailer light legal requirements in the UK.
Are light boards actually legal?
Yes, with a sensible caveat. A board is legal as long as the lamps sit where the regulations expect them: indicators and markers reasonably close to the outer edges, at a legal height, the right colours, and securely fixed. On a narrow box trailer that is easy. On a wide plant trailer or a long flatbed, a single board may leave the indicators too far inboard, and you may also need side marker lights along the length. That is the real reason you sometimes hear “boards are not legal for most trailers”, and it is an overstatement. The board is fine; it just has to end up legal on your particular trailer. If in doubt, measure the width and check our side marker light guide.
7-pin or 13-pin?
For a light board you only need the road lighting, so a 7-pin (12N) board is the usual choice. If your car has the newer 13-pin socket, either buy a 13-pin board or use an adapter. We explain the difference in our 7-pin and 13-pin wiring guide and cover converting between them in our adapter guide.
LED or bulb?
This is the easy decision. LED boards cost a little more up front and pay you back quickly in reliability. There is no filament to shake loose on a bumpy site, they light instantly, they are brighter in rain and spray, and they sip current, which matters on older towing electrics.
| LED board | Bulb board | |
|---|---|---|
| Lifespan | Typically up to 30,000–50,000 hours depending on design | Around 1,000 hours |
| Vibration | No filament to fail | Filaments fail on rough ground |
| Brightness in rain | Bright, instant | Dimmer, slight delay |
| Current draw | Low | Higher |
| Upfront cost | A little more | A little less |
One thing to know: because LEDs draw so little current, some cars read them as a blown bulb and flash the indicators quickly. It is harmless and quick to fix, and we explain it in why are my LED trailer lights blinking.
Fitting and looking after a board
- Strap or bolt the board so it cannot shift, with the lamps level and the plate light over your number plate.
- Keep the plug face clean and dry. A smear of dielectric grease keeps corrosion at bay.
- Check the earth first if anything misbehaves; a poor earth causes most board faults.
- Store it somewhere dry between jobs so the connector lasts.
If a board ever plays up, our fault-finding guide walks you through it step by step.
Can I use a light board instead of trailer lights?
If your trailer already has compliant rear lighting, a separate light board is not normally required. Light boards are most commonly used on small utility trailers, when transporting loads that obscure the vehicle’s lights, or on trailers that don’t have permanently fitted rear lighting.
Browse LED light boards and rear lights
We stock genuine, E-marked LED lighting built for British weather. Have a look at our rear lights and the full LED trailer lights range, or read why waterproof LED trailer lights are worth it. Not sure what fits your trailer? Drop us a line and we will point you to the right board.
