Post supports are commonly sized for square timber posts of 70×70 mm, 90×90 mm and 100×100 mm, with smaller and larger sizes also available. Many holders have an adjustable cradle or bolts that grip a small range of post widths, so measure the actual post and match it to the support's internal dimension rather than the nominal timber size.

Most post supports are made from hot-dip or electro-galvanised steel, which protects them against corrosion for long-term outdoor use. The galvanised zinc coating suits fences, decks and pergolas exposed to rain and ground moisture; for coastal or high-corrosion sites, choose a hot-dip galvanised or stainless option and keep timber slightly clear of standing water.

Installation depends on the type: bolt-down bases are fixed to cured concrete with anchor bolts, concrete-in holders are set into a wet concrete footing and left to cure, and drive-in spikes are hammered straight into firm soil using a driving tool. In every case, keep the socket level and plumb before securing the post, and set it to the recommended depth so the support carries the load correctly.

Whether fixings are included depends on the model: many concrete-in and drive-in supports need only the post screws, while bolt-down bases sometimes come with anchor bolts and sometimes require them separately. GeZu Impex lists the supplied fixings and the recommended post screw pattern for each holder. Load capacity varies with the support type, post size and how it is anchored, so match a heavier-gauge holder to taller fences, decks and pergolas.