Vines are natural plant parts that do not grow by themselves after world generation, but are initial parts of the pre-generated Creativerse template game worlds. On the other hand, Vines can be "grown" by planting Cragwood Saplings - some of the player-grown Cragwood trees will have Vines on them.
While Vines cannot be climbed as long as they are "part" of naturally "generated" Vine-covered Wood blocks (on Cragwood trees and Wildwood trees). But Vines that "hang" freely in Jungles as well as Vines that have been placed by players into the game world can be climbed like ladders. Vines can also be used as cushions to negate falling damage.
Even though Wood blocks are usually flammable, hanging Vines as well as Vine-covered natural Wood blocks as part of trees are fireproof. Vines are crafting ingredients for several crafting recipes and can be made into Twines in a Processor. They cannot be stuck flat onto Wood blocks nor "integrated" into Wood blocks by players.
How to obtain
Vines can be seen hanging from Wildwood trees freely, but they can also be a part of Cragwood blocks and Wildwood blocks on tree trunks and branches where they cannot be climbed but will just look decorative.
When pointing your cursor at these wood blocks, they will be shown as being "Vines". When harvesting these wood blocks (no Power Cells are required for this), either 1 unit of Vines will be collected, 2 unites of Vines, or 1 unit of Vines together with 1 Wood block (either Cragwood or Wildwood).
Vines can additionally occasionally be obtained from common green Leafies, Night Twiggies, Mossy Leafies, Dried Leafies, Autumn Leafies and Night Leafies - either when killing and looting them or when harvesting from them after taming and feeding them. In this way, Vines are "infinite" resources too.
Giant Wildwood trees are probably the best places to collect Vines since these are hanging down from their tree tops by the dozen in the most common types of game worlds (template worlds RW5-8), and these strands of Vines are really long too.
Giant Wildwood trees can easily be spotted on the area map in the shape of white dots in emerald green jungle biomes (with dark brown cross-like clearings), since the giant trees always carry Snow on top.
How to use
You can climb up and down on free "hanging" or placed Vines much like on ladders, and you can place Vines as blocks on top of each other to create natural ladders. Other than that, Vines can be placed as jumping blankets, since they will cushion the fall of player characters and negate all falling damage when landing on them.
Vines can be placed for climbing vertically. It is not hard to place pieces of Vines as ladders on top of each other while climbing upwards without requiring any blocks as a scaffold. However, placing Vines beneath the one the player character is standing or hanging on is extremely difficult, if not completely impossible.
Even if you rotate Vines upside down and connect them, they will keep on working as a ladder like normally. Vines can also be placed sideways and can still be used for climbing this way. They can be combined with Ice Vines that are part of the Frost Bundle and can only be made from a Store-exclusive crafting recipe.
You can climb Vines as a ladder even if you leave free spaces the size of one block in between the Vines, but it's advisable to start with two pieces of Vines stacked on top of each other at the lower base of the ladder, otherwise it will be difficult to start climbing bottom-up.
It is easy to fall from a ladder made from Vines by passing through it if it's not placed against solid blocks, or by taking a step too far sideways; so it is advisable to take care while climbing.
Different from actual ladders, Vines will not give player characters a little push forward on their top side and such cannot be used for the creation of roller coasters. Sometimes Vines can even make player characters jump rather high inadvertently.
You can rotate Vines fully into all directions by holding R (as the default key) while holding and moving the left mouse button. The chosen rotation angle can then be "locked" too by simply typing "r" while looking at a rotated item, then all items of the same stack will be placed facing the same direction.
Unfortunately you cannot attach Vines "flatly" onto blocks like they stick to Cragwood and Wildwood before being harvested. It would require for them to be "integrated" into the Wood blocks in order to create Vine-covered Wood blocks, which is not possible. So you cannot make Wood blocks look like "naturally" Vine-covered trees nor use Vines as a flat decoration on Stone blocks or the like either.
When jumping on a ladder made of Vines or landing on them while flying, the player character will "stick" to the ladder and will not take falling damage if they aim well. Because of this, Vines can be used to negate falling damage when placed on the ground just like all liquids and Blocks of Goo.
Players cannot use Vines to make their way hand over hand along a ceiling anymore since the "Big" update R55 on August 22nd 2018.
Creatures cannot climb ladders made from Vines, however Vines can only be used as a substitute for Fences if you stack at least 3 pieces of them on top of each other, because Creatures can still simply walk over one unit of Vines or can jump onto two units of Vines placed on top of each other just like they would use any kind of cubic block.
Since Creatures can just walk across the upper end of ladders made from Vines, they can also use them as "bridges" to cross small gaps as well if ladders are placed between two blocks.
Standing on a ladder made from Vines does not make a player character invulnerable, even though aggressive Creatures usually ignore player characters who are on a ladder and out of their reach. Many aggressive Creatures will stop hunting the player character as soon as s/he steps up or down a ladder and will then retreat a little. However some aggressive Creatures will follow player characters and then wait in front of the ladder, hitting at the player character as far as they can reach.
Standing on a ladder makes throwing Explosives hard to accomplish, so it usually is necessary to reach the top of the ladder to be able to throw anything accurately.
Like all crafted objects and blocks, Vines can be picked up without the need to equip any Power Cells. Of course you won't be able to pick up such objects on game worlds, on player claims or in Adventures where your Permission rank is not sufficient (mainly when you are merely a visitor), which can only be changed by the owner of the game world, claim owner or Adventure creator. For more details please read the article about Permissions.
Other than that, Vines can also be put on display by placing them into the slots of display containers like Placemats, Stone Wall Shelves, Hidden Temple Altars, Galactic Grav-Chambers, Frozen Containers, Holiday Decorative Trees, Snow Buried Containers, Holiday Mantles, Wood Planters, Flower Pots or the like. Vines will be displayed upright and usually reduced in size in/on such containers. They cannot be rotated while on display, but most display containers can be rotated with all the items "inside" them. Unfortunately, Vines tend to re-rotate into an upright position even if display containers are rotated.
When growing Cragwood-trees from Saplings in a fitting biome (mind that Grassland often does not support trees), sometimes specimen with vines will grow, especially if you had planted 2x2 Saplings or more together. This makes Vines "renewable" resources (also by "farming" them from Leafies), albeit somehow indirectly and not every time, since not every single player-grown Cragwood tree will bear Vines, and not many units anyways.
Other than that, Vines do not regrow by themselves on any type of wood or trees.
Using Vines for crafting purposes
Obtaining Vines is one of the unlocking requirements for the crafting recipe for Thatched Walls in your crafting-menu,
Vines can be used for a number of crafting-recipes like for Wood Swords, the very useful Processor and Wood Chests. Crafting these will then also help with unlocking several other important crafting recipes.
Vines do not catch fire, and Wood blocks with vines on them neither. So even if the leaves and wood from a Wildwood tree will all burn down, the hanging Vines, all blocks of Wildwood with Vines on them, all Cragwood blocks with Vines on them as well as all blocks of Beeswax will still prevail floating in the air. Queen Bees and tree Flowers can burn down to nothingness nowadays though.