All the parts and pieces for the tabernacle were brought to Moses. Moses erected the tabernacle. He placed the Ark in the tent of meeting with its poles in place. He placed the testimony, the two stone tablets inscribed with the Ten Commandments of God in the Ark, then placed the Mercy Seat on top of the Ark. He placed the veil in front of the Ark to conceal it. Then a table with the show bread on the north side, the lamp stand on the south side and let the lamps. He placed the gold altar in front of the veil, and burned fragrant incense on the gold altar. Then he set up another veil for the doorway of the tabernacle.
All of these things represent Jesus Christ. He is the door (John.10.9). He is the bread of life (John.6.35). He is the light of the world (John.8.12). He is the altar and through faith in Him the saints offer prayers to God (John.15.7, Rev.5.8). Behind the veil concealed at that point in time Jesus is the Mercy Seat (Rom.3.25).
Note: In Romans 3.25 the English word propitiation is translated in scripture into English from the Greek word hilasterion; the literal translation is mercy seat.
NASB Strongs Dictionary. (1998). The Lockman Foundation.
New American Standard Bible. (1995). The Lockman Foundation.