Ground spikes are commonly made for square timber posts of 70×70 mm, 90×90 mm and 100×100 mm, with round-socket versions for poles as well. The socket holds a set post size and bolt-through or clamp versions grip the timber firmly, so measure the actual post and match it to the socket's internal dimension. Longer spikes give a deeper anchor and more resistance to leaning on taller fence and pergola posts.

Drive a drive-in spike into firm soil using a driving tool or block that fits the socket, checking it stays plumb as it goes down; screw-in ground screws are turned in with a bar until the collar reaches ground level. Start with a pilot hole in stony ground, keep the socket vertical, then drop the post in and secure it with the clamp bolts or screws. Avoid hitting the socket directly, and don't use spikes in loose, waterlogged or made-up ground.

Ground spikes are typically hot-dip galvanised steel, which resists corrosion where the anchor is buried in moist soil for long-term outdoor use. Hot-dip galvanising gives a thick zinc layer suited to ground contact on fence, garden and pergola posts. In very wet, acidic or coastal soils, expect a shorter life than a concrete-set post, and keep the socket collar clear of pooling water so the timber base stays as dry as possible.

A ground spike's holding power depends mainly on soil firmness, spike length and post height rather than a fixed rating, so it suits light-to-medium fence, garden and pergola posts on firm ground. Increase stability by choosing a longer spike, driving it fully home, keeping the post plumb, and adding bracing or a concrete collar for tall or exposed posts. GeZu Impex lists spike length, socket size and the clamp fixings for each model so you can match the anchor to the load.