What Are These Called?

[Handstitched]

G'Day, I'd like to make a custom  detachable extension for  my sewing machine table  to accommodate  large or long items . 

 But for the life of me I can't seem to find the joiners I need, or what they're called. Forgive the very poor drawing , the bottom part is all wrong, I know ,  but the top part will give you an idea of what it is I'm looking for.  Just two simple pieces that slot into each other . Some on here may have used them to make extensions to round arm  sewing machines  

Thanks for your help

HS 

*this may even go in the sewing machines thread

[chiefjason]

You might have to piece them together.  Which means finding them in person.  Top is a U shaped connector.  For the bottom you could use a free floating shelf bracket that would fit into said connector.  Look into French cleats too.  Not sure the cleat would give you the stability you need though.  

[Handstitched]

34 minutes ago, chiefjason said:

 Look into French cleats too

You've nailed it in one ...woo hoo  thanks friend   

I preceded the  words French Cleats with ' metal' .

HS

[chiefjason]

7 hours ago, Handstitched said:

You've nailed it in one ...woo hoo  thanks friend   

I preceded the  words French Cleats with ' metal' .

HS

 

Cool.  I was coming across different French cleats.  Those look like a better option than what I found.