Van Dale Groot woordenboek van de Nederlandse taal (14e editie, 2005):

"makelaar":

4 (bouwkunde) stuk hout, in de top van een kap aangebracht, dat dient tot verenigingspunt van nok, spruiten en hoekkepers
4a (bij molenaars) rond boveneinde van de grote spil
5 (gewestelijk) houten spits boven aan de top van puntgevels (bv. bij schuren)
6 (bij molenaars) (bij paltrokken) versiering op de achterzijde van de molenkap
7 (gewestelijk) lat op de aanslag van dubbele deuren of vensters
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Onroerend Goed Lexicon :

makelaar (middenstijl dakspant) =
king post, joggle post, joggle piece

makelaar (nokbeëindiging) =
gable post
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Van Dale nl-en:

3 (bouwkunst)
king / crown post

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Note added at 36 mins (2015-08-31 10:53:08 GMT)
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Oxforddictionaries.com:

"king post":

def.: An upright post in the centre of a roof truss, extending from the tie beam to the apex of the truss.

EXAMPLE SENTENCES:
– Bracket sets with two arms support the four-rafter beams; there are straight braces known as timu; and a king post is present in the roof truss.
– In the process, the various components acquired names according to their place in this system - king post, hammer beam, purlin, sill, and so forth - names that are still used today.
– First, as Su notes, a king post is used in the shrine's roof truss.
– Again, two crossbeams with camel's hump-shaped braces support the roof truss, and there is no king post.
– A single king post or several queen posts may be used according to the length of span and the support required.

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Note added at 38 mins (2015-08-31 10:54:57 GMT)
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Nieuw Groot Woordenboek Industrie & Techniek NE-EN/EN-NE (GWIT):

makelaar [3][BUILD.] (m.b.t. dakconstructie) = crown post; wind brace

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Note added at 43 mins (2015-08-31 11:00:37 GMT)
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OED:

king-post

1.1 Carpentry. a.1.a An upright post in the centre of a roof-truss, extending from the ridge to the tie-beam.

1776 G. Semple Building in Water 115 The King-post, h. may be the same.
1817 B. Hall Voy. Loo Choo (1820) 54 The roof was well constructed, the rafters being mortised into the ends of the horizontal beams, and braced to the middle by a perpendicular beam or king-post.
1891 A. White Tries at Truth iii. 15 In building a porch, the king-post is the beam on which the whole structure rests.

b.1.b attrib., as king-post roof, king-post truss.

1845 Ecclesiologist I. 149 Tie-beams, which sustain a low king-post roof.
1886 E. S. Morse Japanese Homes i. 10 [He] fairly loathes a structure that has no king-post‥truss.

2.2 On a ship (see quots.).

1927 G. Bradford Gloss. Sea Terms 95/2 King post, a short derrick mast to support the smaller cargo booms.
1948 R. de Kerchove Internat. Maritime Dict. 385/1 King post. (1.) A short heavy mast which serves to support a boom. (2.) The centerline pillars in a ship's hold. 1961 F. H. Burgess Dict. Sailing 127 Kingpost, a vertical post, sometimes resembling a mast, erected near the hatches, to support and top a derrick boom.

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crown-post

The middle post of a trussed roof, which supports the crown of the roof; the king-post.

1703 T. N. City & C. Purchaser 122 Crown-post, is that Post, which (in some Buildings) stands upright in the middle‥It is also call'd a King-piece.    
1703 Moxon Mech. Exerc. 159 Crown Post‥Also the King-Piece, or Joggle-Piece.
1806 Gregory Dict. Arts & Sc. I. 460.
1823 P. Nicholson Pract. Build. 221.

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Note added at 4 hrs (2015-08-31 15:16:42 GMT)
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Oxforddictionaries.com:

"astragal":

(1A) moulding or wooden strip of semicircular cross section.

EXAMPLE SENTENCES:
"Of the 286 planes, the majority, were simple moldings like common ogees, astragals, beads, hollows and rounds."
"Each panel has attached astragal beading with curved comers topped by a beaded and fluted moulded cornice."

(1.1) Architecture A narrow semicircular moulding round the top or bottom of a column.
EXAMPLE SENTENCES:
"A plain astragal ringed the column beneath its plain cap."
"There is a thick overlapping astragal running round the columns carrying the vaults and arches."

(2A) bar separating panes of glass in cabinetmaking.

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Note added at 5 hrs (2015-08-31 15:20:07 GMT)
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OED:

"astragal"

[(? a. F. astragale), ad. L. astragalus, a. Gr. ἀστράγαλος a huckle-bone (in pl. dice), a moulding in the capital of a column, a leguminous plant. See also astragalus.]

(1.1) Phys. The ball of the ankle-joint; the huckle-bone; = astragalus 1. Hence in pl. (as in Gr.): Dice, which were orig. huckle-bones.

1727–51 Chambers Cycl., Astragal‥a bone of the heel.    
1850 J. Leitch Müller's Anc. Art §391 Eros as Ganymedes' conqueror at the game of astragals.

(2.)
(a.2.a) Arch. A small moulding, of semicircular section, sometimes plain, sometimes carved with leaves or cut into beads, placed round the top or bottom of columns, and used to separate the different parts of the architrave in ornamental entablatures. Also attrib.

1563 Shute Archit. C j a, Nowe at the toppe of Scapus, you shall make Astragalus.
1651 Davenant Gondibert ii. vi. xlvi, From the astrigal To the flat frieze.
1789 Smyth tr. Aldrich's Archit. (1818) 89 An astragal‥has berries often cut on it.
1862 Rickman Goth. Archit. 14 The torus when very small becomes an astragal.
1872 Shipley Gloss. Eccl. Terms 402 Roundel, a bead or astragal moulding.

(b.2.b) (See quot. 1940.)

1858 Skyring's Builders' Prices 33 Astragal sashes.
1940 Chambers's Techn. Dict. 56/2 Astragal, a specially shaped bar used for connecting together glazing bars or sheets of glass in a window. Ibid., Astragal tool, a special tool‥used in wood-turning for turning beads and astragals.

(3.3) Gunnery. A ring or moulding encircling a cannon about six inches from the mouth.

1656 Blount Glossogr., Astragal‥is therefore transferred to the canon.
1692 in Smith Seaman's Gram. ii. vi. 94 The Astragal, or Cornice Ring.
1862 Griffiths Artill. Man., Muzzle Astragal and Fillets.

(4.4) (See quot.) ? Obs.

1725 Bradley Fam. Dict. s.v. Tyles, Scallop or Astragal are used in some places for weather Tyling.
1751 Chambers Cycl. s.v. Tyle, Scallop or astragal Tyles are‥like plain tiles, only their lower ends are in form of an astragal.

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Note added at 5 hrs (2015-08-31 15:21:53 GMT)
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OGL:
aanslaglijst (m.b.t. deur) = astragal

GWIT:
aanslaglijst [BUILD.] = supporting frame

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Note added at 5 hrs (2015-08-31 15:23:31 GMT)
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Van Dale Groot woordenboek van de Nederlandse taal (14e editie, 2005):

aanslaglijst

1· zinken lijst aan de boven- en voorzijde van een behangen kastdeur voor een betere sluiting
1a. lijst die bij dubbele deuren de tussennaad bedekt