There isn’t a grappling device in GKC, but you can make a grappling system (platformer maps).
You need:
EDIT: use a prop instead of a sentry, or if you can’t, just use the sentry.
1+ Sentry
1 Zapper or Blaster
(BTW this isn’t a very good grappling system but it can work)
First, have a platform like this:
Then, get a sentry and place it on the platform. Make sure the health and respawn time is set to 1. Then change the name of the sentry to Grappler:
Now, make a zone where no weapons can be fired, and put it around the sentry so that the sentry cannot fire a weapon.
Get the item image device of a Zapper and cover the Sentry with it.
The final part: Link the sentry to a teleporter to the point so that when the sentry is knocked out, the player is teleported on top of the sentry. (Teleporter should not be visible) Get the Starting Inventory device and set it to a Common Zapper.
Now, when you hit the sentry, you should be teleported there.
You will need to adjust the settings so that this will work (especially the Zone)