A tetrahedron having stiff edges is inherently rigid. Hickory wood is very hard, stiff, dense and shock resistant. Despite reinforcements his progress was painfully slow against stiff opposition. Spines are generally stiff, sharp and unsegmented. The Nasty Boys have a reputation of being very stiff with their opponents. This adds to its mass without making it too stiff. They are fairly stiff to support the foot. This continued somewhat in the third round with Joshua still looking tired and stiff legged. He struggled to move inside his stiff suit. Diaphragm walls are a type of retaining walls that are very stiff and generally watertight. The head has a crown of stiff golden feathers. Hedgehogs are easily recognized by their spines, which are hollow hairs made stiff with keratin. This makes DNA a moderately stiff molecule. Gowns are often puffed out with the use of several layers of stiff tulle. They tended to be stiff and jerky.