Plate compactors fall into one of three categories: single plate compactors that move in only a forward direction, reversible which move in forward and reverse, and high performance/heavy-duty plate compactors. The handle of a plate compactor plays a key roll. It can be mounted in the center or back of the unit. It can be a swinging handle allowing for easier maneuverability. And it could also be an anti-vibration hadle for increased operator comfort. Equipment is a key element in paving and pavement maintenance.
When hovering, hummingbirds hold their bodies upright and flap their wings horizontally in a shallow figure-8. As the wings swing back they tilt flat for a moment before the wings are drawn. Most hummingbirds flap their wings about 50 or so times a second.
Juvenile male ruby-throated hummingbird hovering. This hummingbird is from 7 to 9 cm (2.8 to 3.5 in) long and has an 8 to 11 cm (3.1 to 4.3 in) wingspan. Weight can range from 2 to 6 g (0.071 to 0.212 oz), with males averaging 3.4 g (0.12 oz) against the slightly larger female which averages 3.8 g (0.13 oz).