After crossing a certain point, the elements moves out of the screen revert to the original place

After crossing a certain point, the elements moves out of the screen revert to the original place

Dear all

For private use I'd like to know how the "The Survival Kit" sideways works.
Click on the kit and move it left or right. After the survival kit has passed/moved over a specific point to the left or to right side, the "The Survival Kit" moves out of the screen, shows up on the other side of the screen edge and moves back to the original place.

How the the moves back to the original back works isn't so a problem.... http://jqueryui.com/draggable/#revert...but I don't understand how the image "The Survival Kit" leaves the screen after a certain point moving right or left and comes back on the other side from the screen and revert to the original place (middle of the screen).

Thank you for your help.

Best regards
Thomas