For Christmas I got my grandsons Fort Magic - it is an amazing building kit that you can use to make all kinds of neat forts. We decided to start with the yellow submarine (must be my son-in-law's influence since he is a Beatles fan.)
You can cover them with fabric, sheets, or as one woman suggested online - plastic tablecloths from the dollar store. The problem with the plastic tablecloth is that they tear very easy and with the clips that come with the kit you can use them only one time. I think I will wait for closeouts on material at JoAnn's.
Jackson and Dylan
I did purchase material to make the race car fort and the airplane fort. I think material will be much easier.