One of the three improvements for the Shovel Blade the Charge Handle allows the use of a charged Dig Slash by holding down the attack button. When released the Dig Slash does two damage and pierces through most defenses (such as that of a Hoppicles or Goldarmor). On the other hand as long as the attack is charged Shovel Knight moves far slower unlike the charge attack given by the Dynamo Mail.
Amiibo Mode
The Charge Handle can only be used by Custom Knight by equipping the special move "Shovel Upgrades". However, using a different charge move will disable Charge Handle.