While holding 'Ctrl', pushing the combination of 'W' or 'S' and 'A' or 'D' your character would skate around. This happens when your weapon is up.

Something similar to this happens with your weapon down. If your are walking then push 'Ctrl' and 'A' or 'D', your character will continue forward or backward if you let go of the respective key. This will keep going until you let go of the control and strafe keys.