I am repairing a wood deck and what to know why you would use cleats instead of wood screws?
What is the difference?


Nails are stronger in shear than screws. Screws are harder but more brittle.

I expect most people use decking screws since they are designed for fixing the planks to a frame.

I believe cleats, as in a piece of wood used to fix two other pieces together, are mostly used where you need to hide the fixings or where it would otherwise be difficult to fix the parts together. Cleats can be nailed, screwed or joined in almost any fashion depending on the circumstances.


  how do I know what will work for me?


The easiest way is to follow established convention. Some DIY shops provide leaflets describing how to construct a deck. To fix an existing deck I'd just do whatever the builder of that deck did - unless you have reason to suspect it was poorly built.

More generally, I'd work out what direction the forces were in the finished structure and aim to have those forces transmitted across wood on wood joins running perpendicular to the force.

This

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not this

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