Keys can be either wood or metal. But all of them are different inserts in the slot between the two beams and are designed to increase the strength. This mount is provided with an additional steel bolts that can pass as a key, and did not affect her, squeezing just beams.
Wooden dowels.
Depending on which part of the tree trunk was used in the manufacture of pins, isolated longitudinal, transverse, oblique and longitudinal keys at a stretch.
The resistance across the grain is much smaller than along them, so the cross keys are not very popular. Cross are called because the grain direction is perpendicular to the keys to the fiber direction of both beams.
Longitudinal keys provide a more solid mount. Grain direction keys here coincides with the direction of the fibers of beams.
Longitudinal oblique keys require some precision sockets. Most often, they are at an angle of 45 °. They provide even greater strength beams, not allowing it to bend once in two directions: up and down.
Keys with a stretch used where necessary to strengthen both the beam and increase internal tension. To do this in the slot between the beams are driven in two keys at once, with wedge-shaped. Both keys must be packed to go.
The metal keys are recessed and fit wheel, annular or square.
Retractable keys are used for side mounting of multiple parts. Keys for sure hollowed socket, then set itself key, and then the whole structure is tightened bolts.
For molded tongues is preparing to nest, they are fixed and then close the other half of the structure. Also, the fixing bolts.
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