hardwood, supports, posts
楨 centers on sturdy wooden structural elements: hardwood used for supports and posts that hold things up.
楨 combines 木 (tree/wood) with 貞, which likely contributes the sound and may carry a sense of uprightness or firmness, fitting the idea of a sturdy wooden post.
The wood radical 木 on the left and 貞 on the right suggest a firm, upright wooden post. Picture a hardwood beam standing straight like a loyal guard.
For テイ, imagine a sturdy wooden table (テーブル) leg: the first syllable テイ echoes the reading, and the hardwood post supports the table.