The appeal of the slingback is not that it makes a shoe more formal. It is that small bit of exposure at the heel loosens a pump without making it feel casual, which is why the shape can move between a sharp outfit and something less planned. The products here show how much the finish changes the mood: Jeffrey Campbell's Booshky Slingback Pump keeps things straightforward, while Aeyde's Liza Snake-Effect Leather Slingback Pumps make the same outline more graphic. JW Anderson's Buckle Velvet Slingback Pumps are a different proposition again, all texture and hardware. There is even a flat in Gianvito Rossi's Robbie Leather Slingback Flats, a useful reminder that the strap is not the point if the shoe does not suit the day. Fit is the deciding detail. Check that the heel stays anchored when you walk, and pay attention to the height you will actually wear, not the height that photographs well. A slingback should feel like a choice, not a tiny negotiation with your shoe.