Finish It Act This bill requires the Department of Defense (DOD) to submit a plan (within 15 days after the bill is enacted) to utilize, transfer, or donate to states all existing excess border wall construction materials to construct a permanent physical barrier along the U.S.-Mexico border. If DOD delays in submitting or executing the plan, the travel budget of the Under Secretary of Defense for Policy must be decreased by 1% for every two days of delay. DOD must work with the Defense Logistics Agency to execute the plan until DOD is no longer incurring any costs to maintain, store, or protect the excess materials. Any state requesting border wall construction materials must certify, in writing, that the materials will be used exclusively for the construction of a permanent physical barrier to stop illicit human and vehicle trafficking along the border. If a state does not use all such materials for the specified purpose within two years of receiving the materials, the state must pay the federal government an amount equal to the original purchase price of the materials.