LG GD910 User Manual page 192

Getting to know your phone
2 hold the watch strap and pull the "A" part of the buckle
vertically.
3 hold the watch strap and adjust the strap length by
moving the "A" part of the buckle from side to side.
4 To fix the strap length of watch, push the "A" part of the
buckle back to the original location.
5 Press the buckle until a 'click' is heard.
1 LG GD910 | User Guide