Single Open Ended Jaw Spanner Non -Sparking Secure Tools's open-end jaw spanner, as the name suggests one end is open which provides to hold the nuts or bolts heads or grip that to either tight or lose it. Open-end spanner is also known as single-end spanners their known size is basically the difference between their respective jaws. The selection of spanner would be the subject of based on the nut & bolts sizes to be used.