What are weld clamp magnets used for? 
        
welding a tree shaped candle holder together with an arrow fixed multi angle weld clamp magnet

Weld clamp magnets are predominantly used to hold pieces of ferromagnetic materials in position for tack welding.
 
Tack welding is where a series of small welds are used to align pieces of metal securely before completing with a final weld.

A ferromagnetic material is a term for anything attracted by a magnetic force. To be ferromagnetic it must contain a element of iron, nickel, cobalt, or gadolinium 
        
Welding a bicycle frame with an arrow fixed multi angle weld clamp magnet

Weld clamp magnets can help to weld together things such as steel gates, metal stair steps and bicycle frames.
 
Inside and outside corners produced by a corner fixed multi angle weld clamp magnet on a sheet of steel   
They can be used to create the inside and outside corners of box section steel as they can hold metal at a variety of different angles.
 
Box section steel is a square or rectangular hollow steel box used for general fabrication and construction.
 
Soldering two pieces of metal together that are held at a right angle with an arrow fixed multi angle weld clamp magnet   
Weld clamp magnets can also be used to hold thin pieces of metal together at different angles to allow them to be soldered together.
 
Soldering uses a melted alloy to form a thin layer between the two pieces of metal to join them together.
 
Layout work on a hexagon shaped steel structure with multiple magnetic square fixed multi angle weld clamp magnets 

They can be used as supports for steel structures whilst doing layout work. Layout work is a process where reference points are marked across pieces of metal in order to create a template.
 
The template on the metal is carried out before starting to alter the steel structure in any way e.g. drilling holes into it.