life drawing cross reference

so we had did a drawing of a 10 min of the model in standing position just go get warmed up and then we where introduced to cross references where you would have to drag out a line of a cetacean body part to  cross another part of the body  which meant to help to keep the proportions and the figure should show up in the lines eventuality but i had some problems with that the lies didn't seams to be joining at the right places and over all it just confused me. I ll need more practice to understand and be able to adapt this in to my drawing

got frustrated with most of them