Thumb Watering Can This thumb watering can is ideal for the gentle watering of delicate seedlings and small plants. First, put the thumb watering can fully under the water and let it fill. Place your thumb on the hole at the top. Take it out of the water and hold it above the seedling or plant you want to water. Remove your thumb from the hole, and water the plant. Place your thumb back over the hole to stop the fine shower. – made from terra cotta – ideal for seedlings – easy to use