Aligning to the holes – The patented hole pattern on the TETRIX^® structural pieces enables you to attach pieces together at an angle, not just horizontally and vertically from each other. For example, you can attach a piece at 45°.

Tightening screws – The TETRIX hole pattern is on all sides of the structural pieces – making it easy to tighten the screws with the hex key by simply putting the wrench through the other side as shown at right.

The screws in the TETRIX system are fastened with kep nuts, which feature a toothed side. This toothed side should face toward the screw so the teeth can grab onto the metal, which helps it hold better.

Selecting screws – There are two sizes of socket head cap screws (SHCS) in the base set: 1/2" and 5/16". As a rule, use the 1/2" screws for joining two structural elements together. Use the shorter 5/16" screws to attach tube clamps to structural pieces or when there isn’t much clearance on the inside of parts.

The 3/8" button head cap screws (BHCS) are useful when the SHCSs might stick out too far from the body and rub against a moving part, such as a gear. Use BHCSs to attach servos to servo brackets.

Tightening tube clamps – For maximum clamping grip, tighten the clamp screws in stages. First, snug the set screw on the clamp – but not too tight. Then, attach the clamp to the structural element with four screws and tighten them partway. Finish tightening the set screw, and then finish tightening the four other screws. This will keep the clamp in the proper shape for attaching to structural elements while ensuring proper grip on axles and tubes.

Tightening the set screw axle hubs – When tightening these hubs, be sure to tighten the set screw – using the 3/32" hex key – against the flat side of the axle.