John Gill Commentary Ezekiel 21:19

"Also, thou son of man, appoint thee two ways, that the sword of the king of Babylon may come; they twain shall come forth out of one land: and mark out a place, mark it out at the head of the way to the city." — Ezekiel 21:19 (ASV)

Also thou, son of man, appoint thee two ways, that the sword
of the king of Babylon may come
Describe or draw out upon a table or tile, as in (Ezekiel 4:1) , or on the ground, two roads, such as are described in maps; which it may be supposed the king of Babylon would take, either the one or the other, in order to make war against some king or another:

both twain shall come forth out of one land ;
both ways must be drawn as coming from one country, even Babylon;

and choose thou a place, choose it at the head of the way to the city ;
fix upon some spacious place, where Nebuchadnezzar may be supposed to bring his army, as a proper rendezvous for them to muster them in; and let be where two ways meet, that lead to cities, one to one city, and another to another:

and it seems that upon the desert of Arabia, through which the king of Babylon came, there was such a place, where two ways met, and one led to Jerusalem, and the other to Rabbath; and this is the place the prophet was to describe, and where in fact Nebuchadnezzar came.