YOU SAID:

I never knew hot dogs were make out of rubber

INTO JAPANESE

私はホットドッグがゴムで作られていることは知らなかった

BACK INTO ENGLISH

I did not know that hot dogs are made of rubber

INTO JAPANESE

私はホットドッグがゴム製であることを知らなかった

BACK INTO ENGLISH

I did not know that hot dogs are made of rubber