Decorex Hardware Ball Top Post Cap – Standard 4x4 Lumber (Actual 3.5"x3.5") The 4x4 post is the most common post in residential construction — fence lines, deck railings, gate frames, mailbox posts, garden borders. They go up by the dozen and they take a beating year-round. The top of every one of them is exposed end grain — the single most moisture-vulnerable surface on any wood post. Left uncapped, moisture penetrates the core and rot works its way down from the inside out. By the time damage is visible, replacement is the only option. Decorex Hardware caps seal that exposure completely. Installation: 2 stainless steel screws with black-coated heads included. Can also be secured with exterior-grade construction adhesive or silicone for a completely fastener-free finish. Installs in under two minutes per post with no special tools. Suitable for residential, commercial, and contractor applications. Compatible applications: fence posts, deck railing posts, gate columns, mailbox posts, lamp posts, garden post pillars, newel posts, pergola posts. Important: This cap fits ONLY standard 4x4 dimensional lumber posts with actual dimensions of 3.5"x3.5". It will NOT fit true full-dimension 4x4 posts that measure 4"x4". Always measure your post before ordering — do not rely on the lumber label. Decorex Hardware — Canadian-designed outdoor hardware built for real weather, real use, and lasting curb appeal. Material: Aluminum.