Sometimes you know you are going to sell a bike (or bikes) on a given date.  

Or you may want to close your store to rentals after a certain time.

But you are actively renting the items right now so you don't want to set them as unavailable yet.

In both cases you will want to create a 'blocker booking'.  A reservation that prevents the item(s) being booked from that date.

Simply make a reservation containing the item(s) in question, for a period of time.

You will then either sell on the items, or make them available again.