Hi Sue - I think this site can walk you through it:
Hope this helps:
If you want the whole post, you could use the fence post and one rail between that come at home improvement stores for making pole/post fences. It would make a darling hitching post, western style. However, if you only want ONE post, you could attach a metal ring on a fence post. That is what I would do. This would be like the old South when they had a single post for hitching a horse. I would use a post made especially for a mail box post holder and go from there. Hope this helps, Sue.
That should be a pretty simple build with 4x4s joined together with lag bolts but the posts should be set in concrete. I'd first set the 4x4 posts in concrete and once set run a leveling string between the two and trim as needed. Then attach a cross 4x4 on the top with lag screws through the top. Alternatively you could attach a 2x4 to ether side of the 4x4 with lag bolts.