Strange rocks obtained by training Construction are part of the Dahmaroc statue. Two strange rocks from each skill are required to complete the statue, which can be built once per week. Strange rocks may be stored inside a statue collection bag.
Any Construction activity (in regular or building mode) that would garner Construction experience (building furniture, making flatpacks) while in a player-owned house. They may be obtained while using protean planks, which make a favorable option as they stack in your inventory. To conserve resources it is advised to build something that uses low amount of planks.
Building limestone fireplace and oak chair flatpacks gives strange rocks most quickly and for comparatively low cost, at 486 and 1,118 coins, respectively (assuming items are bought from the Grand Exchange). Oak lectern only requires one plank, but cannot be made as a flatpack. Flatpacks can also be traded in with Advisor Ghrim once all of the Hard Rellekka tasks have been completed, allowing some of the loss to be recouped.
- Idling in a player-owned house was the only way to receive construction rocks before an update on 4 August 2010.