Handmines were used on the planet Skaro during the Thousand Year War. They appeared in groups, and would take hold of and pull individuals underground. They resembled hands with an eye in the centre of the palm. They could be destroyed by a Dalek gunstick.
They travelled by tunnelling under the earth and possessed incredible strength; a single handmine was able to pull an adult Kaled beneath the earth with considerable force.
They were drawn to sound and movement. If a person was still but making noise, they would rise up from the ground to search for the target. Once they had found someone, they would turn to face them.
As a child, Davros found himself surrounded by handmines. A soldier named Kanzo tried to help him, reminding him to stand still before being pulled underground. The Twelfth Doctor found him, but abandoned him when he discovered who Davros was. The Doctor later returned and used a Dalek gunstick to destroy the Handmines surrounding Davros, rescuing him and bringing the boy home so he could teach Davros the concept of mercy. (TV: The Magician's Apprentice, The Witch's Familiar)
When helping the young Davros, the Doctor showed an awareness of Handmines by reciting the survival rate of an encounter (one in a thousand) without being aware he was on Skaro. This implies Handmines were native to, or used on other planets. (TV: The Magician's Apprentice)