The diagram shows that FG = IJ are congruent segments due to the double tickmarks. These are the hypotenuses of the right triangles. 
So that takes care of the "H" in "HL". 
The L stands for "leg", so we need to have a congruent pair of corresponding legs. 
Due to the orientation of the triangles, it's not clear how the corresponding legs match up, but if any of the following is true
- EF = IK
 - EF = JK
 - EG = IK
 - EG = JK
 
then we'd have enough to use HL.