A Juliet balcony is a non-trafficable balustrade. There is no platform behind it for someone to stand on. It exists to let full-height doors or floor-level windows open safely on upper levels. The balustrade meets the same fall-protection rules as a real balcony (1000 mm minimum height, 125 mm maximum gap in residential), but the door swings against it rather than out onto a deck.
Fixings are usually expansion bolts into structural brick or concrete, or onto a steel back-plate welded to the building's structural framing. Loads are calculated for the full balustrade design load even though nobody stands behind it. The worst case is someone leaning hard against the rail from inside.
CAD60's Juliet balcony model takes any balcony width and computes baluster spacing, fixing positions, and dimension lines.