Carabiners are new to some people. If so, within ACL 4.0, they can be used to test new learning that is a reasonable expectation because the cues are visible.
(The plastic loops are easier to use than the carabiner. The plastic strip is threaded through holes, such as the circles formed by pony tail holders. Attention is directed towards threading the hole, which is similar to putting a needle through a hole when stitching in the ACLS-6.)