Expanded metal sheet with square holes has higher percentage of open area than expanded metal sheet with diamond holes. This is why it is frequently used for air ducting as part of air conditioning. Expanded metal sheet with square holes is generally supplied as flattened material whose edges are not, as a rule, so sharp. This makes them easier to fit into frames. Square holes in expanded metal sheet do not protrude as is the case of classical diamond holes.
Expanded metal is manufactured according to DIN 791 standard.