How to join a vertical and horizontal pole?
&quot;Structural pipe fittings&quot; seems to be the most common generic term for that.  Note that it may be difficult to find a lot of selection of 1/2&quot; hardware, because the typical use for this stuff is constructing railings, and railings need to be thicker than that, but there's probably some 1/2&quot; stuff out there.  McMaster has some options that might work for you here.  Other search terms for similar types of pipe clamps that may work for you are &quot;kee klamp&quot; and &quot;cheeseburough&quot;.