How do you fill a sieve with water?
Filling a sieve with water sounds like one of the tasks you might encounter while reading a fairytale. Something along the lines of picking out a wagonload of poppy seeds from black flour dust or telling the king how many hairs he has on his head. In the case of the person assigning the task in fairy tales and myths, they do not expect the person to succeed and even hope for failure.
In the case of koans, inviting someone to fill a sieve with water is something that is suggested knowing that the person can accomplish the task and may even have already accomplished it, though they don’t know it themselves. The task is our life and we are always living it, whether we notice it or not. Our life may feel like a sieve full of holes, as we feel unable to hold onto anything. But not being able to hold onto anything is just the way life is, the way a sieve cannot hold onto water.
We can spend a lot of time trying to plug up the holes of our life/sieve and may even succeed in being able to make it hold water, but then it is no longer a sieve and it is no longer life. To fill a sieve with water it is to appreciate that like the cracks that let the light in, holes in a sieve, in our life, let the light in too.