The poem circles around the act of signing a document, and it treats that small act as something heavier than it looks. The title points to an old idea that a thing's outward marks reveal its nature, and here the "mark" is handwriting. The speaker calls ink "the first forced temple," which suggests that writing is a kind of shrine built under compulsion. Signing isn't entirely free; something is demanding it.
The second stanza sounds almost proud. Handwriting is "as personal as" anything can be, so signing an agreement means putting yourself on the page. But the last lines complicate that. The speaker makes "the state a copy / with great seeming art," and the word "seeming" is the catch. The copy looks skillful, yet it may be a performance, perhaps even a kind of forgery or show of obedience. The mood is quiet, guarded and a little uneasy. The speaker gives the authorities what they want, but it's unclear how much of the self goes along with it.