A fine wire passes between the fibres of a woven fabric; a heavy one cuts them.

On fabric under tension a severed thread becomes a run that spreads from the fixing.

That failure appears weeks later rather than at installation, which is what makes it expensive.

The practical rule is the finest gauge that will hold the tension.

That is the opposite of the reasoning for construction staples, where holding power dominates.

Heavier gauges are still used on webbing and hessian, where the material is not the show face.

Narrow for show fabric, wider for webbing, hessian and linings.

A narrow crown disappears under fabric or trim and concentrates enough pressure to hold without bruising.

A wider crown grips loose-weave and structural materials better.

Webbing in particular needs a wide crown, since it carries real load.

Crown width is part of the tool system, so it is largely decided when the tool is chosen.

Most upholstery work uses more than one staple size for exactly these reasons.

Short - there is only a thin frame rail behind, and a long staple comes through or splits it.

Frame rails are much thinner than the timber that construction staples go into.

A staple through the far side is a hazard and a defect.

Splitting matters more than usual because the frame is reused across successive re-covers.

Old holes accumulate, so a frame that splits early has a shortened life.

Hardwood frames may need a shorter or finer staple than softwood ones.

In practice yes - manual, electric and pneumatic tackers each have their own staple system.

Crown width, gauge, leg length and collation are all tool-specific.

A staple that fits the magazine may still jam or drive inconsistently.

Driving power matters as much as fit, since an underpowered tool leaves staples proud.

Proud staples catch on fabric and have to be set by hand, which is slow.

Buying tool and consumables as a system is the straightforward approach.

Steel for interior work, stainless for marine and outdoor upholstery.

A rusting staple stains the fabric around it permanently.

That defect shows long before anything comes loose, and it cannot be cleaned out.

Marine, garden and vehicle upholstery are all damp environments in practice.

Stainless is also used where a natural fibre will be dampened during cleaning.

Galvanised staples are a middle option but the coating can be damaged during driving.

Yes - every old staple should come out, and it is most of the labour in a re-cover.

Old staples left in place stop new fabric sitting flat and tear it as it is tensioned.

They also occupy the positions the new staples want.

Staple removers and pincers are the usual tools, and the frame is inspected as they come out.

A frame with too many accumulated holes may need repair before it will hold again.

Broken staples left below the surface are the ones that cause trouble later.

Set them by hand with a hammer and punch - a proud staple catches fabric and shows under a finish.

Underpowered tools and hard frame timber both leave staples standing.

Setting them individually is slow, which is why tool power is worth getting right.

Adjusting the tool's drive setting is the first thing to try.

On very hard frames a pneumatic tool may be the only practical answer.

A staple that cannot be driven flush is better removed than hammered repeatedly, since repeated blows bruise the surrounding timber.