So was up flying practice approaches under the hood. Safety pilot who is working on his Instrument rating asks me a bit of a stumper today. When I fly SP for him one of the questions that he asks a lot is when to fly a procedure turn and how. For RNAV and VOR approaches I’m pretty good with that info. So we are flying to a towered class D field. Approaching from opposite side of final course. The ILS does depict a bold line “race track” style hold (not missed hold) at the IAF. He asks me if we need to fly that course reversal or PT?? I say no because we are talking and being vectored onto the final approach course. But it got me thinking... when do I need to fly that bold line turn/hold??I could only come up that I would fly it if tower was closed and not getting vectored to final. I was going to ask the departure controller but they were a bit busy today The RNAV procedure turn is easy no questions there.