Road signs, Double bend
What does the double bend warning sign mean?
A double bend ahead, first one way then the other.

A red triangle with an S-shaped road.
What you must do
Slow down and be ready to steer through both bends, keeping left.
Where you will see it
Winding roads with two bends close together.
Test yourself
The theory test asks you to recognise signs like this one. Try the road and traffic signs quiz (with an easy and a hard set), or read the signs revision notes. Source: Know Your Traffic Signs.
Other common road signs
Meaning based on Know Your Traffic Signs and The Highway Code. The sign image is an official Department for Transport sign (Crown copyright) from Wikimedia Commons, reused under the Open Government Licence or the public domain. Always check the current Highway Code on gov.uk. Not affiliated with or endorsed by the DVSA.