These Detectors are an invaluable addition to any DIYers toolbox, if you drill a wall for a fixing and hit a hidden pipe or live cable, it can be an expensive and frustrating mistake to make.
They are simple to use, first read all the instructions so you fully understand how it works as there may be different settings for each material to be detected, they usually have solid or flashing leds to show a pipe, cable or stud has been detected, this is sometimes accompanied with an audible tone.
It is good practice to use your new detector on a wall where you know a pipe, cable or wall stud is present, so you can get conversant with which light, or tone combination alerts you to what is present in the wall.
There are various detectors on the market which can be purchased for around £15 to £30.