Oma plata or Sankaku Garami (triangular entanglement) in Judo is a great submission of your opponents front deltoid. The main difference between an oma plata and an ude garami is the fact that you are using your legs as the machanism to apply the submission as opposed to your arms.
Below are a few of my setups i use to finish my opponent with oma plata.
Oma plata from turtle
Oma plata from a failed juji gatame attempt
A Fantastic setup into Omaplata