What must a security agreement in writing have

1) an agreement 2) authenticated - signed or symbol with intent to adopt 3) in writing 4) Reasonably identifies the collateral - 3rd party must be able to identify - numerous similar items need serial number of collateral - Cannot construe what is identified from perfection docs - specific UCC definitions work - even if don't mean to grant but do with words, courts will say you did - burden is on one alleging security agreement to show there is one - if ambiguous it is construed by state laws - mistaken date makes unreasonable to identify