1 Therein two gates were placed seemly well:
two gates > [the mouth and the anus] seemly > fittingly (i.e. in opposition)
2 The one before, by which all in did pas,
before > in front pas > pass; pace
3 Did the other far in workmanship excel; 4 For not of wood, nor of enduring brass, 5 But of more worthy substance framed it was;
framed > fashioned, made
6 Doubly disparted, it did lock and close,
disparted > divided (i.e. into upper and lower jaws)
7 That when it locked, none might through pas,
That > [So that] pas > (Takes the meaning alternate to that of "pas" in line 2, thus allowing the rhyme)