Foot placement on throw-in

[helpme]

I understand the rule for a throw-in states part of each foot must be on or outside the touchline. My question is, can part of one or both feet be in the field of play. For instance, one foot is outside the touchline and only the heel of the other foot is touching the touchline with the remaining part of the foot over the touchline and in the field of play. i was always taught the both feet must be entirely on or outside the touchline.

Thanks in Advance