| Barnes' Notes on the Bible For the joinings - i. e., the girders, or cramps - pieces of iron to be used in joining beams or stones together.
Clarke's Commentary on the BibleIrons - for the nails, etc. - Iron for bolts, bars, hinges, etc., etc.
Gill's Exposition of the Entire BibleAnd David prepared iron in abundance for the nails for the doors of the gates, and for the joinings,.... Great plenty of iron to make nails of for joining the boards together, of which the doors and gates were to be made, and for the fastening of the hinges of them: and brass in abundance without weight; for making the altar of brass, and the laver of brass, and other vessels. Brass was much used by the Heathens in sacred things, as Macrobius (p) observes. (p) Saturnal. l. 5. c. 19.
Keil and Delitzsch Biblical Commentary on the Old TestamentIron and brass he prepared in abundance: the iron for the nails of the doors, i.e., for the folding-doors of the gates, i.e., partly for the pivots (Zapfen) on which the folding-doors turned, partly to strengthen the boards of which doors were made; as also for the מחבּרות, literally, things to connect, i.e., properly iron cramps.
Geneva Study BibleAnd David prepared iron {c} in abundance for the nails for the doors of the gates, and for the joinings; and brass in abundance without weight; (c) That is, which weighed fifty shekels of gold, 2Ch 3:9.
Matthew Henry's Concise Commentary22:1-5 On occasion of the terrible judgment inflicted on Israel for the sin of David, God pointed out the place where he would have the temple built; upon which, David was excited to make preparations for the great work. David must not build, but he would do all he could; he prepared abundantly before his death. What our hands find to do for God, and our souls, and those round us, let us do it with all our might, before our death; for after death there is no device nor working. And when the Lord refuses to employ us in those services which we desired, we must not be discouraged or idle, but do what we can, though in a humbler sphere. | 
