How do afternoon tea types cut sandwiches?

[PETRONELLAS]

I’m fascinated how the edges are so perfect, bread not squished, filling not oozing. Is it ‘just’ a very sharp knife? If so, what sort of knife?

A bread knife, using the sawing action and the serrated edge to cut the bread, rather than much downwards pressure.

Decent bread knife, no pressing down to cut, wipe between cuts so no filling traces on the outer bread surfaces. I usually cut the crusts off before filling.

A very, very sharp chefs knife, don't apply pressure.