Bay Window With Arch . .and discovered that the window sash had originally been painted black! Find top design and renovation professionals on. Full and Bow Arched Windows Mambakofi Finest Timber Joinery from www.mambakofi.co.za The purpose of a bay window is to admit more light than would a window flush with the wall line. We also create custom tailored master pieces for our clients. Your bay window, which follows the unique style, also gives the entire kitchen a delicate impression.