The monoplata is a super-powerful armlock related both to the omoplata and the Kimura armlocks. For the monoplata you use your legs and your body to create a powerful torque on your opponent’s shoulder. From https://www.grapplearts.com/omoplata is a breakdown of the arm and leg positions that’ll make your monoplata armlock super powerful!

00:15 Actions of your left (basing) hand
00:28 Actions of your right (top) leg
00:40 Actions of your left (bottom) leg
00:58 Actions of your right (near) hand
01:24 How to apply the monoplata
02:13 The outside-ashi style of monoplata