For the engine component, see Rocker cover

A rocker box (also known as a "cradle") is a mining implement for separating alluvial placer gold from sand and gravel. It consists of a high-sided box, which is open on one end and on top. The inside bottom of the box is lined with riffles and a usually a carpet similar to a sluice

Sluice

A sluice is a water channel that is controlled at its head by a gate . For example, a millrace is a sluice that channels water toward a water mill...

. On top of the box is a classifier sieve (usually with half-inch or quarter-inch openings) which screens-out larger pieces of rock and other material, allowing only finer sand and gravel through. Between the sieve and the lower sluice section is a baffle, which acts as another trap for fine gold and also ensures that the aggregate material being processed is evenly distributed before it enters the sluice section. It sits at an angle and points towards the closed back of the box. Traditionally, the baffle consisted of a flexible apron or "blanket riffle" made of canvas or a similar material, which had a sag of about an inch and a half in the center, to act as a collection pocket for fine gold. Later rockers (including most modern ones) dispensed with the flexible apron and used a pair of solid wood or metal baffle boards which. These are sometimes covered with carpet to trap fine gold. The entire device sits on rockers at a slight gradient, which allows it to be rocked side to side.

Today, the rocker box is not used as extensively as the sluice

Sluice

A sluice is a water channel that is controlled at its head by a gate . For example, a millrace is a sluice that channels water toward a water mill...

, but still is an effective method of recovering gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 in dryer than usual areas. Like a sluice box, the rocker box has riffle

Riffle

A Riffle is a short, relatively shallow and coarse-bedded length of stream over which the stream flows at higher velocity and higher turbulence than it normally does in comparison to a pool....

s and a carpet

Carpet

A carpet is a textile floor covering consisting of an upper layer of "pile" attached to a backing. The pile is generally either made from wool or a manmade fibre such as polypropylene,nylon or polyester and usually consists of twisted tufts which are often heat-treated to maintain their...

 in it to trap the gold. It was designed to be used in areas with less water than a sluice box. The process involves pouring water out of a small cup and then rocking the small sluice box like a cradle

Cradle

Cradle may refer to:Mechanical devices:*Bassinet, a small bed, often on rockers, in which babies and small children sleep* Ship cradle, supports a ship that is dry docked...

, thus the name rocker box or cradle.