- The vertical buttonhole is the most common, and when the garment is buttoned up, the button will be at one of the edges of the buttonhole. This type of buttonhole should therefore start 3 mm (1/8") outside of centre front line (or whatever line you're aligning your buttons at).
- The horizontal buttonhole is mostly used for shirt fronts buttoned up with many small buttons. Different rules apply for this one, but sometimes the buttonhole starts 3 mm (1/8") above the button marking. The top button in a shirt is often sewn in so it meets the top of the buttonhole. The rest of the buttons are lined at the middle of the buttonhole, with aligned holes.
- The general rule for buttonhole length is that it should be equal to the button diameter plus the thickness plus 3 mm (1/8"), but for the bound buttonholes we skip the extra 3 mm (1/8").
A bound buttonhole should not be wider than 6 mm (1/4"), so each inset is 3 mm (1/8"). My book also tells me to sew all the buttonholes at once, finishing the same detail on each buttonhole before moving on to the next detail. Apparently that's the trick to get them identical! There's different ways of marking up the buttonhole, but I have to say the method I've used for my test was very convenient, marking both edges and the centre front with machine basting. This technique is of course dependent on your fabric, and you shouldn't use it if the stitches will show after you've pulled the thread out. Hand basting with silk thread will be better for fine fabrics.
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