Wood – Refilling extra space between rail and posts for inserting screws

fencewoodwoodworking

I'm working on a wooden fence, similar to the picture below. It has a 2"x4" wood rail that will be the length of all four 4"x4" pressure-treated wood posts. This rail will be attached to the posts with screws.

Since the concrete where the posts are attached to is uneven, there will be "empty" space between rail and some posts in-between.

What can I use to fill that unwanted space that's strong enough to insert screws? I don't have the tools to cut the 4"x4" posts to the correct height, so that's out of the question.

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Best Answer

The right solution is to trim the higher posts, which can be done with a simple hand saw. You could clamp some blocks on the posts below the cut to act as guides, keeping the cut square and preventing accidental damage due to slips.

The only acceptable alternative (to my mind) is a shim cut of a suitable material, such as wood with the grain oriented across the post. This is actually a more complex task. You haven't said what the dimensions of the gaps are or what finish you need to match, so I can't offer a more specific suggestion.