Portable forge

Portable forge is an item won on Treasure Hunter that acts as both an anvil and furnace when planted. Using the forge provides 10% additional experience to most smithing actions (does not provide bonus experience when smelting corrupted ore). The furnace provides a 5% chance of providing an extra bar while the anvil has a 10% chance per bar of saving each of the bars in use (this includes protean bars). All bars saved are deposited in the bank whether your inventory is full or not. When this happens, the following shows up in the chatbox: or

It can be placed anywhere that you can light a fire and is both visble to and usable by all other players. It cannot be placed in a Player-owned house. It cannot be placed in an ongoing fight of Vorago, regardless of being able to light a fire there. It vanishes after placed for 5 minutes. Although you can still use the forge after it disappears if you have clicked on it, you will no longer receive any of the benefits of the forge. When the Forge disappears, if you are Smithing, you will be stopped unless, curiously, smelting protean bars or corrupted ore. However, this may be an oversight by Jagex.

Profitability
Depending on Grand Exchange prices portable forges may yield more profit per hour compared to other methods like Superheat Item, the Blast Furnace, or regular anvils.

The supplies for 1,000 rune bars (1,000 runite ores, 8,000 coal and 16 portable forges) cost coins. The forge would produce a total of 1,053 rune bars, worth coins, with a profit/loss of  coins, or an hourly profit/loss (759 ores smelted per hour) of  coins.

Used purely for smithing bars for experience, the forge can significantly reduce costs. 1,000 rune bars smithed into platelegs and sold on the Grand Exchange would require 13 forges and save 111 bars, resulting in a profit/loss of coins, or an hourly profit/loss of  coins (3105 bars smithed per hour) or  coins per experience, and 232,875 experience per hour.

Note: The above calculations do not take the effects of wasteless smithing into consideration.

If a player decides to buy the ores (1,000 runite ores, 8,000 coal and 29 portable forges), smelt the bars and process them into platelegs the forges would produce an extra 175 rune bars. This results in a total profit/loss of, or an hourly profit/loss of. Additionally high alchemising the resulting 391 platelegs would change the total profit/loss to and the hourly profit/loss to.

Trivia

 * It is possible for wasteless smithing to activate together with the forge's bar saving ability.
 * On 15 June 2015, a bug was introduced that allowed players to use the portable forges in order to block players, preventing them from moving. This has since been fixed.