This is a simple mod but a must have in survival servers.
Hook: hit on a edge to climb up.
Upgraded hook: use with double hight
Rope: place on a edge to climb, or throw it.
Locked rope: only you can take it, or throw it.
Slingshot: throw junk far away and hurt your enemies place it to change side to use
Mouth breather assembly: use outside water/vaccum to refill with air, use in water/vaccum to refill your breath (max 10 times))
Pchest: portable chest, the stuff is stored inside the chest/tool, and not in a ghost inventory.
Simply awesome for spelunking and mountaineering
If you want to explore caves how they were meant to be explored (which is not towering cobble up to get higher!), this mod takes the stage. If there's a cliff or a ledge you want to get up on, just throw your grappling hook up there and climb up! This has made spelunking a lot more fun for me, since I like to explore rather than mine a lot of the time :)
Additionally, this mod adds a few other nodes other than the ropes/hooks - The PChest is a portable inventory (which can be quite useful to store your ores on a mining trip, as well as many other applications), there's a mouth breather assembly in case you want to venture far into the ocean, and a slingshot for throwing stuff at other players/mobs!