multiple meanings do exist.
one of them: me, your Lord and God, being the keystone.
Resting on the base of the Apostles and prophets, Christ Jesus himself being the chief keystone
Ephes 2:20
Because it is said in the Writings, See, I am placing a keystone in Zion, of great and special value; and the man who has faith in him will not be put to shame.
1 Pet 2:6