Types of check valves. A ball check valve is a check valve in which the closing member, the movable part to block the flow, is a spherical ball. In some ball check valves, the ball is spring-loaded to help keep it shut.
(October 2016) Learning is the act of acquiring new, or modifying and reinforcing existing, knowledge, behaviors, skills, values, or preferences which may lead to a potential change in synthesizing information, depth of the knowledge, attitude or behavior relative to the type and range of experience.
Repetition is not the only factor is learning, but it's a key factor and often under appreciated. Let me know your experiences with repetition via the comments link below. And don't forget; repetition is the mother of all learning.