It's possible to set a default margin for a freight contract as a pricing guideline for the sales reps.
Open the contract draft and in a contract header click on 'Show margins':
A table will appear below:
Add default margins for each container type as shown and publish the contract.
Now, when a sales rep wants to use this contract in a quote, the default margin will be automatically applied. This will act as a pricing guideline, the sales rep will always be able to adjust the margin.