I'm trying to make a gate structure for my attic to prevent people from falling through the pull-down stairs opening. For this, I'm joining threaded iron piping together with elbow joints and t-joints. The problem is that when I try to make a rectangle with four sections of pipe and four elbows/t-joints, I can't attach the fourth corner together because tightening the fourth section of pipe into the fourth joint by turning it clockwise would un-screw the third joint because it would be turning counter-clockwise.

Here is a photo of what I'm doing:

enter image description here

I feel like I'm missing something obvious. And when I googled it, I found this site for building shelves with similar materials and a similar method, but it doesn't mention the problem I'm having.

Could someone please help?

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    Most folks that build the iron pipe type structures for shelves and such do not try to build the pipe into square or rectangle shapes. In the link that you provided if you look closely at the pictures you'll see that the guy has generally not inserted the threaded pipe ends fully into the fittings. So lets say he as used 3 turns of insertion for each joint. To make the last side of the rectangle he would screw in one end of a pipe a total of 6 turns and then go to the last corner and screw the pipe in 3 turns. This makes the other end come back out 3 turns leaving a uniform insertion depth. – Michael Karas Jun 6 '16 at 1:14
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    You can also make things out of copper pipe. All the fittings there are slip joint and solder together. Others use PVC pipe for projects like this and that has slip joint fittings that are welded with PVC cement. – Michael Karas Jun 6 '16 at 1:16
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    I just saw a closet system on This Old House last week use this method and I had the same question! – Evil Elf Jun 7 '16 at 17:52

you need a "union" connector. It allows both sides to tighten and then tighten union.

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  • google.com/… – Wayfaring Stranger Jun 6 '16 at 0:36
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    Unions work great for this application but they do get a bit spendy compared to the other elbows and tees. – Michael Karas Jun 6 '16 at 1:19
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    A union is large and maybe ugly compared to a left-hand thread nipple and coupling, which works kinda like a union and will be less obtrusive (however it will be more $$). – Jimmy Fix-it Jun 6 '16 at 1:24

If you don't want to have this problem with the last connection, the other option is to use "structural pipe fittings" that clamp onto the pipe instead of using threads. enter image description here

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