-all four-

[ formerly, All` four".] All four legs of a quadruped; or the two legs and two arms of a person. [1913 Webster]

To be,
go, or
run,
on all fours (Fig.), to be on the same footing; to correspond (with) exactly; to be alike in all the circumstances to be considered. “This example is on all fours with the other.” “No simile can go on all fours.” Macaulay. [1913 Webster]