Power shears and nibblers make straight or curved cuts in sheet metal or other thin materials. Sheet metal shears move their pivoting blade against their fixed blade to cut flat or corrugated panels and ducts. They cut more slowly than nibblers but leave smoother edges and less mess. Sheet metal nibblers punch a series of small holes to cut flat, corrugated, or uneven sheets. They leave shavings and rough edges but cut tighter curves and more precise corners than shears. Carpet and leather shears roll their circular blade along surfaces to slice through carpet, leather, cardboard, and other soft materials. Cement board shears cut like scissors through fiber cement siding and sheets.