01
Save the supporting details
Keep the supplier, product name, origin information provided, dimensions, thickness selection, and purchase date together. Retain pallet or lot labels when available. Similar descriptive names can be used for different products, and names may change over time. A photograph of the label beside a representative slate can connect paperwork to the material more clearly than an invoice alone.
02
Make the record usable
Give the owner a copy and store another with the building's maintenance documents. Note which roof slopes received each lot if more than one was used. Keep representative spare pieces labeled without marking the visible face. When a future repair is needed, these records provide a starting point for a current match rather than a guarantee that the original product remains available.