a house of cards

A house of cards is a structure made by leaning playing cards against each other to form a replica of something. No glue or adhesives are used, hence it is very flimsy and readily collapses. The term is used to describe plans which are not based on something sound and hence are easily collapsed.

Can I use it this way?
First thanks a lot,but I still can't understand it completely.Can I use it this way:What you have planned is just a house of cards.

If what is planned is based on unsound premises, you are using it correctly. For instance, the plan might assume that everyone will be free to go on the same date even though this is very unlikely.

Thanks
Thank you very much! I can understand it well now.