Copper block 50mm (2") square made of high purity solid copper for puddle welding with your MIG. Trying to fill small holes can be frustrating but one of these makes it easy. Just hold against the back of the hole you are welding and the MIG will fill the hole instead of firing yards of wire through the hole! The weld won't stick to the block, which is machined on all sides to be perfectly smooth so it makes contact with as large an area of the panel as possible. This dissapates heat away from the weld area, reducing the risk of distortion in your panel.
Everyone working with car body panels should have one!
C&B Tip: Don't confuse with thin competitor items with magnets inside to stick to the panel 'hands free' they just collect steel fragments and then don't contact the panel for heat dissapation.
SAFETY: Wear welding gloves when holding!