The Heavy Sieve allows sifting of Compressed Blocks with a small loss. It requires a suitable mesh to function.
Right-clicking the Heavy Sieve with a mesh will insert it. It can be retrieved by shift-right-clicking the block with an empty hand.
Once a mesh has been inserted, the sieve can be right clicked with siftable blocks to sift them.
In Ex Nihilo Omnia, an [Iron Mesh](excompressum:Iron Mesh) is required to sift blocks. Any lower level mesh will break instantly on use in a Heavy Sieve.
In Ex Nihilo Adscensio, any mesh will work, as meshes in Adscensio have no durability and only split the loot table.