ANSWER: To do modeling assignments you do not have to be tall and thin.
Tall and thin does help a model to do a bit more work. However, certainly in no way, if a model is NOT tall and thin, is she restricted from getting modeling bookings. As a matter of fact, most models are not tall and thin at all.
Many models have more than 2,000 pictures of themselves in their possession. This does not mean that the models knows how-to-pose. Sadly, most models will argue that they do know how-to-pose.
THE RIGHT FACIAL EXPRESSION CAN MAKE OR BREAK YOU GETTING RE-BOOKED FOR AN ASSIGNMENT.
YOU MUST KNOW HOW-TO-POSE IN ORDER TO SUCCESSFULLY GET BOOKINGS FOR PRINT WORK. DOING JUST ANYTHING, EVEN THOUGH YOU MIGHT LOOK GOOD, WILL NOT GET YOU RE-BOOKED FOR A MODELING JOB.
Models dream about being on a billboard for an advertisement.
However, most models are also freelance models. The majority of models booked in PRINT ADVERTISEMENTS are often models who have representation and/or management from a modeling agency.
Print ads are put together from advertising agencies. And in turn, most ad agencies ONLY hire models that have representation by a modeling agency.
Most freelance models are not eligible to even be submitted for print ads because they are not represented nor managed by a modeling agency. So if you are a model and you want to get booked for print ads, at least work with a modeling agency so that you can be submitted for a print ad booking. Once in a blue moon a freelance model might be booked for a print ad. However, in most cases, advertising agencies will inform the model to contact them once the model has representation from a modeling agency.
Call up a few advertising agencies and try to submit yourself. You will frequently be turned down and told that you have to have representation from a modeling agency.