removing the cab??

Ok guys i've never had the cab off my truck yet, but it is coming off tomarrow and i am wondering do i just need to loosen the bolts from the bottom or is there a nut on top to??

The bolts are held on with two nuts so you can take the bottom one off no problem then you can break loose the second one without holding the top of the bolt but at some point you can just use vice grips to keep the top off the bolt from not spinning and finish off taking the second nut