The Filson Smooth Bone Slip-Joint Knife is This Smooth Bone Slip Joint pocket knife employs a traditional slip-joint to keep it open, a design that?s been proven for centuries. Its simplicity is its strength, with no complex locking mechanisms to fail. Rust-resistant high-carbon steel blade sharpens easily and holds its edge well. The narrow profile and smooth bone handle slips in and out of pockets easily. Lanyard hole to prevent loss. Drop point blade geometry. Filson exclusive.