If your vendor allows adding 'Delivery Instructions' to your orders, please add the following sentence:
"Delivery ONLY in BACK, between BLDG 9 and 11. in BAY 1 Hipshipper "

Below you can see how to add it to an Amazon order.

In the 'Checkout' page, click 'Change' to edit the 'Shipping Address'

Then click the 'Edit address' link

Find and click the 'Add preferences, notes, access coded and more' link

Scroll down to the last option, 'Do we need additional instructions to find this address?'

Finally, paste the line "Delivery ONLY in BACK, between BLDG 9 and 11. in BAY 1 Hipshipper " into the field

And then click 'Use this address' to continue and finalize the order.