What are steel post stiffeners?

Trex Fencing posts typically do not need stiffeners or inserts. The exceptions would be for fences taller than 8' and for the hinge side of a gate. Two types of post stiffeners are used with Trex fencing and gates. 

C-Channel Hinge Post Stiffener (TPFI)

This stiffener is designed for use with gates up to 6' tall and widths up to the Large Standard size (65-1/2" wide), and that have a fence section on the opposite side of the gate hinge post*. One end is open to allow the brackets for a section of fence to be attached on the opposite side without interference. The 12-gauge galvanized steel is available in 9' lengths. 

* A section of fence on the opposite side of the hinge post helps to keep the hinge post plumb by acting as a counter balance).

Heavy Duty Post Stiffener (TPFIHD and TFPIHD12)

This stiffener is used for large gates, fences taller than 8', when the hinge post is a standalone post, and when a fence line does not run parallel on the opposite side of the hinge post.

The heavy duty stiffener can be embedded in a concrete pad with the Trex composite post sleeved over the top. The 7-gauge (.188" thick") square tube is made of galvanized steel. Note, a ring is welded inside the square tube. This does not serve any purpose for the installation of a Trex fence. It is used to hang the tube as it is dipped for galvanization.  The heavy duty stiffeners are available in 9' (TFPIHD) and 12' (TFPIHD12) lengths. Self-tapping screws will need to be used when attaching fence brackets  (if applicable) to the hinge post.

Note: Heavy duty hinges are available for gates larger than 6' wide and with heights more than 6' tall.