Men's Three-Piece (Suits & Blazers)

A waistcoat cut from the same cloth as the jacket and trousers turns a two-piece into a three-piece. The waistcoat is the sleeveless buttoned garment worn over the shirt. Its purpose is to keep you looking dressed after the jacket comes off.

Most have five or six buttons, with the bottom one left undone, a habit that began as a fit fix and stayed as convention. The back is where cost shows: a lining-fabric back with a metal adjuster buckle is standard and cheap. A back cut from the suit cloth costs more and is the only version that looks right in shirtsleeves. Armholes are cut high and close so the shirt does not billow out at the sides. The hem must cover the trouser waistband completely, even with your arms up, since a strip of shirt showing between waistcoat and belt is the classic error.

Two-piece suits are cooler, cheaper and more current for daily office wear, and nothing about the third piece makes a suit better. It makes it warmer and more formal. A double-breasted jacket covers the same shirt front and waistband with one garment rather than two, which is the smarter answer in summer. Note also that black tie uses a cummerbund or a low-cut evening waistcoat, not an ordinary suit waistcoat.

Weddings, winter formality, and jobs where the jacket comes off at your desk but people still see you all point here. Lean and average builds carry the extra layer without looking thicker. Above 75 degrees Fahrenheit it becomes a burden, since a waistcoat is effectively an unventilated extra layer over the chest. Short-waisted men should be careful too, because very little room sits between the bottom button and the waistband and the proportion crowds fast.

Try it on with your arms overhead and watch the hem, since that is the moment a short waistcoat exposes the shirt. Decide honestly whether you will be seen without the jacket, because that answer alone determines whether a lining back is acceptable. Press it rarely and never over the metal buckle at the back, since a hot iron on metal leaves a permanent mark in the lining.