Abstract: A block window system includes an array of glass or acrylic blocks, a window frame and a variable-dimensioned border frame that positions the array within the window frame. The border frame includes a body that has a first end that is shaped to mate with the array of blocks, and a second end that mates with the window frame, which is a desired size or is sized to fit in a given opening. The height or width of any or all of the sides, the top and the bottom sections of the border frame are adjusted by selecting the length of the body of the corresponding section of the border frame, such that the border frame extends between the interior dimensions of the window frame and the exterior dimensions of the array.