How to use a lead bossing stick

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Bossing sticks are usually used to form internal and external corners.

Bossing an internal corner

Step 1 – Stiffen internal corner

Use a bossing mallet to support the internal corner. You will use your bossing stick to carry out the external shaping of the lead.

The first blows should be directed inwards by the mallet to stiffen the internal corner.

Step 2 – Strike lead

Bossing an internal corner involves losing lead. The direction in which the blows are struck using the bossing stick will determine the direction in which it is driven.

Strike the lead up away from the base of the corner to drive it gradually towards the top edge.

Step 3 – Remove surplus lead

You will find that you have an excess of lead at the top of the corner.

Cut off this surplus lead using snips.

Bossing an external corner

Step 1 – Position sheet lead

After the fold lines for the upstand have been created using a setting-in stick or dressing stick, position the lead against the structure it will be moulded around.

Bend the lead along the fold lines so that it is roughly in place.

Step 2 – Strike lead with bossing stick

With your bossing stick, apply blows around the entire area, initially concentrating on the new corner being formed.

Directing the lead to the corner will help it to maintain a uniform thickness and prevent it from splitting where it is stretched.

Step 3 – Work lead away from corner

After you have formed the external corner, gradually work the lead towards the edge (in this case, downwards), to smooth the material covering the entire area.

Step 4 – Trim off surplus lead

You will know if your bossing has been successful if you see surplus lead being moved gradually away from the corner.

Like for an internal corner, any excess lead should be removed using sheet metal snips. You may also need to trim the lead to ensure that its edges are smooth and neat.