Travel to Isafdar and head to the West side. The best way to do this is by chartering a ship, Catherby is a good location to do so. Use the map below to make your way to the catapult guard. Ensure that you've brought all the materials required (listed above) to save yourself from banking.
A rotting catapult and a Tyras guard will be stationed in this area. Speak to the guard and he will tell you to see General Hining in the Tyras Camp just South of where you are.
Speak with General Hining and offer to repair the catapult. He will inform you that the Catapult Engineer is "somewhere in the forest" and you will need to find him. He will also hand you a letter to deliver to him.
Using the map in step one, getting through all the traps in the forest, make your way to the engineer. Talk to him and he will give you the catapult schematics. Read them and if you have the planks and nails with you the parts will be created. You must also have the saw, knife and hammer in your inventory to make them.
Talk to the engineer again and read the letter. You will need to retrieve the metal parts to the catapult from Rolad, a dwarf wearing blue in a building near the entrance to the Dwarven Mines just next to Ice Mountain.
Make your way to the entrance of the Dwarven Mines, North-east of Falador. Inside the building, you will find and he will tell you all the parts have been dispatched to Port Sarim.
After you have spoken to Rolad, make your way over to Port Sarim and speak to Thaki, who's in the nearby pub. Thaki will not believe that you are a sailor, so head outside and search the drunken sailor to retrieve his hat. Equip it and speak with Thaki again to recieve the catapult parts.
Repairing the catapult
Saw, Hammer, Knife, Catapult parts
The easiest way to get back to Isafdar is to take the charter boat from the Port Sarim docks. Make your way back to the Tyras guard with all the parts and repair the catapult. You must have your saw, hammer and knife with you in order to put the parts back into place on both sides.
After you have completed both sides, talk to the Tyras guard and he will tell you to test the catapult. Adjust the direction and counterweight in order to fire the catapult at all three rocks. You can do this as many times as it takes and then talk to the guard once the three rocks have been destroyed.
Congratulations! Quest Complete!
Guide Made by: Yolk
Corrections submitted by: Yolk, Max, Dx1438, Tugboat, Panda, Majinvegito3, Sytze, Flyte, Umbra