Cottage window kit icludes-
1 roll50m x 6mm lead strip
1 boning tool
1 pattern sheet
watch the video tutorial to see how this pattern is created.
To estimate how much lead you will need- use a marking pen and divide your window into rectangles (eg- 4 across and 5 down) then measure the lengths diagonally passing through the corners of the rectangles. measure each diagonal line from left to right then multiple that by 2 to get the meterage for 1 side of the glass. If you wish to apply the lead to both sides of the glass then double the figure again.
This kit comes with a template however this may not suit every size window, you can make the diamonds as large of small as you like using the rectangle method I just described. You can also add extra patterns and colours with this design (see the last image)