S4S means surfaced on all four sides and E4E means eased four edges. Put them together and you get a board with all four corners, eased and surfaced. These are commonly used for tie downs and side slats in trailer or truck decking applications.
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Contact
(503) 557-7296
695 SE 1ST Avenue
Canbury, Oregon 97013
U.S.A.
email: wood@kayu.com