We have Baxely and Wheeldock chocks. They both work very well. The Baxely has a cradle and a good tug is required to engage/disengage the wheel from the cradle. This is more than the women would like. This is where the Wheeldock comes to the rescue: it has a gas operated rear-facing clamp that is "cocked" and rests on the floor. The rider simply rolls forward until the front wheel rests in the chock, and then steps on a lever, which releases the rear clamp. The wheel is then caged. This system takes up a bit more room than the Baxley but works well.
Someone posted that S-hooks should be avoided and this is sound advice. However, if one has to use them, a bungee cord stretched between the s-hooks at each end of a strap will keep them in tension if the bike shifts.