Rusty swords are broken swords that need repair. They may be taken to Tindel Marchant at the harbour of Port Khazard in the Antiques Shop Stall to be polished and made into usable swords for 100 coins or repaired on a whetstone or on an armour stand in a player-owned-house. However, using a whetstone holds the risk of the sword breaking. When fixed, you will receive a random sword, from bronze to rune, with iron being the most common. This can be beneficial for lower level players who are low on cash. Successfully repairing a rusty sword gives 25 Smithing experience. The sword can be a sword or longsword.
The type of sword most frequently produced from the whetstone varies according to your Crafting level. Higher Crafting levels result in a higher chance of receiving a higher tier sword. The levels are:
Before an update in 2006 that removed finding items in random locations such as boxes, hay bales, and chests, they could be found by repeatedly searching boxes, along with other useless junk like buttons, broken armour, needles, and a few coins. This led some players to spend a lot of time searching the boxes by Tindel Marchant for rusty swords, and then having Tindel fix them. However, after the update, this was no longer possible.