Every Celtic knot starts as a plait: bands crossing over and under, all the way across. Draw a wall across it and the bands turn back there instead of crossing, and the plait becomes a knot. Drag on the grid to draw walls, click a point to turn it, and watch the knotwork weave itself, always over, under, over.
Mirror what I draw
Drag along the grid to draw a wall of breaks. Click a point to switch it from crossing, to horizontal break, to vertical break.
Save
The address of the page keeps this knot, to share it. The grid is never saved in the image.
Grid
Start from
Look
Bain's method
In Celtic Art: The Methods of Construction (1951), George Bain showed how the knots of the Book of Kells and the Pictish stones were laid out: a grid of dots, a plait drawn through it, and "breaks" placed along the grid lines. Wherever a break crosses the plait, the two bands are cut and joined the other way. That is all this page does.
Why it always weaves
The crossings sit on the sides of the grid cells, like the squares of a checkerboard. A band going down and right is over on the vertical sides and under on the horizontal ones, so it alternates over and under. When it turns back at a break it skips one crossing but changes direction too, so it still alternates. However you draw the breaks, the knot is always a true weave.