Universal fenestration cap system and method

A structure opening assembly comprising:

• a structural base having a first side, a second side, and a third side, wherein the second side is perpendicular to the first side and the third side;
• a fenestration cap comprising:
• a substantially flat and continuous base, having a to surface and a bottom surface, said bottom surface being over the second side of the structural base;
• a top linear side generally parallel to the fenestration cap base and having a top surface and a bottom surface,
• a fenestration cap first side extending downwardly from the top side beyond the fenestration cap base, wherein the fenestration cap first side is perpendicular to the top side and the fenestration cap base and wherein at least a portion of said fenestration cap first side serves as a flashing,
• a support extending between and interconnecting the fenestration cap base to the to linear side, said support being opposite the first side,
• a key extending perpendicularly from the fenestration cap first side, said key being substantially planar with the to linear side, wherein the key has a lower surface being a vertical distance above the upper surface of the fenestration cap base, and
• a mounting flange extending perpendicularly from the first support and is substantially planar with the fenestration cap base, wherein a channel is defined by the mounting flange, the first support and a portion of the to linear side that extends beyond the first support, and wherein the to surface of the to linear side is configured to receive at least a portion of a window or a door system;
• and
• finish elements applied to the structural base and adjacent to the fenestration cap and received by the lower surface of the key, and applied within the channel.