When putting crossed braces on a structure to keep it from racking (as used when making a trestle), the most important lashing is the diagonal lashing, which gets its name from the fact that the wrapping turns cross the poles diagonally.

A diagonal lashing is used when there is a need to close a gap between two poles where they cross each other but do not touch.

The traditional diagonal lashing is tied as follows:

Cinch the poles together by tying a timber hitch around them where they cross.

Make three to four wrapping turns on the opposite diagonal to the timber hitch. Keep the wraps parallel to one another and pull them tight.

Make three more tight wraps across the first three, again keeping them parallel.

Take two to three frapping turns between the poles, tightly around both sets of wraps and complete the lashing with a clove hitch around one of the poles.

IX A. The diagonal lashing gets its name because the wraps form a diagonal where they cross the spars. It’s primary use is to spring together two spars that are not touching when the ends are lashed in place on a structure (as in a trestle).

IX B. The trestle is a basic component of many pioneering projects. When we speak of a trestle, we’re referring to what has been dubbed an H-trestle. The way it’s designed yields a very strong supporting structure that is often used as a subassembly for something larger, and frequently serves to support the walkways of a bridge.

OBJECTIVES

Each Scout will tie a diagonal lashing to effectively spring together the X-brace of a trestle.

Working individually or in small groups, Scouts will properly construct a trestle.

MATERIALS

two 6-foot x 2 to 3-inch spars and 15-foot lashing rope for demonstration

six Scout Staves for every four Scouts (six will be needed for each trestle)

two 6-foot x 1/4-inch manila lashing ropes for every Scout (eight will be needed for the square lashings on each trestle)

one 10-foot x 1/4-inch manila lashing rope for every Scout (one will be needed for the diagonal lashing on each trestle)

PROCEDURE A

Using the 6-foot spars and the 15-foot lashing rope, Instructor demonstrates a diagonal lashing, then using a 10-foot lashing rope and two Scout Staves, with the aid of an instructor and following the basic four steps, Scouts will tie a diagonal lashing.

Cinch the poles together by tying a timber hitch around them where they cross.

Make three wrapping turns on the opposite diagonal to the timber hitch.

Keep the wraps parallel to one another and pull them tight. Make three more tight wraps across the first three, again keeping them parallel.

Take two frapping turns between the poles, tightly around both sets of wraps and complete the lashing with a clove hitch around one of the poles.

PROCEDURE B

With eight 6-foot lashing ropes, one 10-foot lashing rope, and working individually or in a group of up to four individuals, Scouts will follow the following procedure and build a trestle:

Lay out two poles parallel to one another as the trestle legs.

Place a pole over the legs at the top and bottom to serve as the ledgers, and then lash them to the legs with four tight Square Lashings using the 6-foot lashing ropes.

Turn the legs and ledgers over and place one pole diagonally over two of the legs as one of the X-braces.

Where it intersects, join this pole to the legs with two tight square lashings.

Place the last pole diagonally OVER one leg and UNDER the other leg, as the other X-brace.

Where it intersects, join this pole to the legs with two tight square lashings.

Stand the structure up. There should be a gap between the the two X-braces where they cross in the middle.

Using the 10-foot lashing rope, spring the X-braces together with a tight diagonal lashing.

The completed trestle should be sturdy enough to be lifted and shaken without losing its shape or becoming loose. After building their trestles, Scouts are ready to have a Roman Chariot Race.