A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
exo 27:1ALTAR FOR BURNT OFFERING. (Exo. 27:1-21)
altar of shittim wood--The dimensions of this altar which was placed at the entrance of the sanctuary were nearly three yards square, and a yard and a half in height. Under the wooden frame of this chest-like altar the inside was hollow, and each corner was to be terminated by "horns"--angular projections, perpendicular or oblique, in the form of horns. The animals to be sacrificed were bound to these (Psa 118:27), and part of the blood was applied to them.
exo 27:3shovels--fire shovels for scraping together any of the scattered ashes.
basons--for receiving the blood of the sacrifice to be sprinkled on the people.
fleshhooks--curved, three-pronged forks (Sa1 2:13-14).
fire-pans--A large sort of vessel, wherein the sacred fire which came down from heaven (Lev 9:24) was kept burning, while they cleaned the altar and the grate from the coals and ashes, and while the altar was carried from one place to another in the wilderness [PATRICK, SPENCER, LE CLERC].
exo 27:4a grate of network of brass--sunk latticework to support the fire.
four brazen rings--by which the grating might be lifted and taken away as occasion required from the body of the altar.
exo 27:5put it under the compass of the altar beneath--that is, the grating in which they were carried to a clean place (Lev 4:12).
exo 27:6staves . . . rings--Those rings were placed at the side through which the poles were inserted on occasions of removal.
exo 27:9the court of the tabernacle--The enclosure in which the edifice stood was a rectangular court, extending rather more than fifty yards in length and half that space in breadth, and the enclosing parapet was about three yards or half the height of the tabernacle. That parapet consisted of a connected series of curtains, made of fine twined linen yarn, woven into a kind of network, so that the people could see through; but that large curtain which overhung the entrance was of a different texture, being embroidered and dyed with variegated colors, and it was furnished with cords for pulling it up or drawing it aside when the priests had occasion to enter. The curtains of this enclosure were supported on sixty brazen pillars which stood on pedestals of the same metal, but their capitals and fillets were of silver, and the hooks on which they were suspended were of silver also.
exo 27:19pins--were designed to hold down the curtains at the bottom, lest the wind should waft them aside.
exo 27:20pure oil olive beaten--that is, such as runs from the olives when bruised and without the application of fire.
for the light . . . Aaron and his sons--were to take charge of lighting it in all time coming.
exo 27:21shall order it from evening to morning--The tabernacle having no windows, the lamps required to be lighted during the day. JOSEPHUS says that in his time only three were lighted; but his were degenerate times, and there is no Scripture authority for this limitation. But although the priests were obliged from necessity to light them by day, they might have let them go out at night had it not been for this express ordinance.