The shape of a written visual guidelines document
A visual guidelines document for merch is not the same document as the corporate brand book, although it can live inside one. The corp book is the source of truth for colour names, logo construction, typography and tone. The merch guidelines sit underneath, and they translate those rules to substrates, decorations and production tolerances. Without that second document the brand book reads as aspirational, and the apparel comes back from the supplier with the colour off by two Delta-E units, the logo on the wrong panel, and the clear space collapsed because there was no rule for the chest pocket placement.
The first section of the merch guidelines is colour. The brand book names colours; the merch guidelines name how each colour is reproduced on each substrate. A navy that is one Pantone in print becomes two Pantones on a metalised substrate, three Pantones across cotton and poly blends, and a CMYK build on ceramic. None of these are wrong; they are the correct technical translation of the same brand colour across surfaces that mix ink into fibre, paint into metal and ink into glaze. The point of the document is to set the tolerance around each reproduction, and to specify which one is the master reference for a given product category.
The second section is placement, which is where most brand books are silent and most merch fails. The chapter should set the clear space around the logo on a chest panel, a sleeve, a back yoke, a cap front and a tote, including the safe area inside any seam or stitch line. It should specify the maximum and minimum scale of the logo relative to the garment, and the orientation for each placement. The chapter should also specify how secondary marks and product-line marks compose with the master logo, and where they sit when both appear on the same garment. None of this is graphic-design invention; it is a set of rules that turn an artwork file into a production ready drawing.
The third section is decoration. Embroidery, screen print, digital print, deboss, foil block, laser engraving and pad print each impose their own constraint on the artwork, the colour count and the substrate. A logo that is at home in flat screen print on cotton is unreadable as a single-colour embroidery on a knit; a mark that is sharp in foil block on a leather cover is illegible in deboss below a certain depth. The decoration chapter lists which method is approved for which product category, the minimum line weight that survives the chosen method, and the maximum coverage before the substrate is compromised.
The fourth section is typography. Many brand books specify a typeface family for headings and body, but few translate that family to embroidery thread weight, foil block width, or engraving line depth. The merch guidelines should specify the approved typefaces for each decoration method, the minimum readable size in millimetres, and the approved substitutes when a thread or foil choice cannot hit the named family. This is the chapter that turns "use the corporate sans serif on the inside cover" into "use a 3 mm tall version of the corporate sans serif in matching foil, or a substitute from the approved fallback list."
The fifth section is photography. A merch programme that ships correct garments and posts the wrong photographs on the website has lost the brand expression. The photography section sets the background, the lighting direction, the camera angle, the colour reference card placement, the post-processing tolerance and the format standards for product imagery. It is the only section that ties the apparel programme to the wider brand world visible to a non-event audience.