If you have seen flat bed trolley or any other you would have known wheels casters form their bases. When using a trolley you would have always thought that its structure decides the amount of weight it can carry. However this is not true, for it is the casters wheels which decide the amount of weight a trolley can be used to carry.
Besides the amount of weight there is one more thing you need to consider when buying two shelf trolley etc, and that is the surface on which you are going to use them. Wheels casters come in different varieties for smooth and rough surfaces. Check them to make the right buying decision with regards to flat bed trolley.
However if you need to also store your things, then you can always consider trolleys which also allow you to store your materials. And if you have specialized items to store and carry then you need to use special storages, like pelican cases can be used to transport electrical items which might get damaged due to water. For your tools you have the option to use plastic tool box with tray or without tray as the need may be.
There is no shortage of materials handling equipments for storage and transportation of your goods, no matter how big or small they are, no matter how heavy or light weight they are. However how good that particular flat bed trolley or pelican cases will be will depend on the type of trolleys or storage equipment you buy.