wrote in message
...
Say I need to deliver 20 amps to a circuit. Is is possible to use two
10 amp wires tied together to do this?

No, for the obvious reason that if one wire worked loose you would still
have a circuit, but it would be grossly overloaded.

I made a 150' extension cord by cable tying a 14/2 extension cord and a 16/3
cord together with cable ties; using one for the hot and the other for the
neutral. If one conductor worked loose I might have excessive voltage drop,
but it would be safe. Still not legal, but safe.
(I got the extension cords at a going out of business sale for 80% off, but
they were the largest they had.)