Roll your tool box off pavment go anyware, over dirt, sand etc. So you can work anyware. The outrigers start all of the way in ,then they can slide to 9 inchs out and then 18 inchs out for full stability. The outrigers lock into place in 3 positions. This is a chasis for your tool box , it will make your tool box much stronger. If you buy an inexspensive tool box this will make it much stonger and ther for last longer. This unit is custom made for each toolbox or tool cart .It is based on total outside dimetions front and side and load capasity.