Girth: This is the measurement around the dogs chest.
Front: This is across the front of the dog. From behind the leg joint on one side to behind the leg joint on the other side. This measurement will be the exact measurement of the front part of the harness.
Shoulders: This is the measurement across the top of the dogs shoulders. This determines at what height the “Front” of the harness will sit. Usually from the top of the leg joint on one side to the top of the leg joint on the other side.
Top: The measurement between the dogs shoulder blades on their back.
S-Front: This is the measurement for the width of the dogs chest. Measured from leg join to leg joint.
This is an example for my large Border Collie.
Girth: 68cm
Front: 42cm
Shoulders: 32cm
Top: 12cm
S-Front: 12cm