Throughout this discussion, I will refer to the person being measured as the model.
Perhaps the greatest challenge when measuring is finding points on the body and consistently using the same ones. There are many measurements that refer back to specific lines or points. It will save you a ton of time to keep these lines and points consistent as references.
When you use elastic, you want it snug so it doesn't move during the entire measurement process. However, you don't want it to deform the body underneath.
What Does Parallel to the Floor Mean?
When the instructions say parallel to the floor, that means that if you measured from the elastic in the front to the floor and the elastic in the back to the floor the measurements would be the same. The elastic is level and not tipped.
You will mark all the points in the diagram following the instructions below.
First, we're going to find the natural waist. Take a piece of elastic and pin or clip it around the waist so that it is snug enough not to slide. Have the model do a few side bends so the elastic will move to the position on it's own. The elastic will not be parallel to the floor, and that's okay for this measurement.
The natural waist is going to seem high, particularly on men. A good point of reference is that the natural waist is close to where the elbow is. Don’t put the elastic where you usually wear your pants or skirts. Patternmaker Pro drafts take the high, natural waist into account when the patterns are drawn.
The waist elastic will stay in place throughout the measurement process. It is used extensively for reference.
Next, put the chain or string around the neck. You don't want it too snug or hanging way down. You want the chain to lay where a collar would meet the neckline of a shirt. This is quite high on the neck. The chain/string should be in the pit of throat at center front.
Next you need to quarter the model. You can use the marker or the crepe/vinyl tape for this. Create a line down each side that splits the body. Center it as best you can. If done correctly, the line should represent the side seam on your garments. This is referred to as the Side Line in the measurement instructions.