Green’s Dictionary of Slang

1. reaching rudely across the table to grab what one wants, rather than asking for it to be passed.

1909		E.L. Sabin ‘What Did Duncan Do?’ in Lippincott’s Monthly Mag. (Phila.) Dec. 724: The subject was not mentioned at breakfast; nor was anything else, in particular, mentioned. Duncan was extremely polite, and passed her the toast when ordinarily he would have permitted her to help herself (true, it was a small table, for two, and easily spanned, but she objected to a ‘boarding-house reach’), and was wholly affable.
1933		Wash. Post 15 July 3: Instead of the old ‘congregate’ dining room, with hundreds of patients making one grand rush for seats, and using the old boarding-house reach for their foodstuffs, usually served to them cold as a landlady’s heart, the men and women now go into those cozy little dining rooms that surround a main kitchen.
1933		Wash. Post 16 Sept. 17: The football training table, banned by the Big Ten grid officials after causing a storm that nearly shattered the conference, may come back with all its trimmings and boarding house reaches.
1937		A. Kober Having Wonderful Time (1975) [play script] 55: Excuse my boarding-house reach.
1998		(ref. to mid-19C) Wash. Artillery of New Orleans – 5th Company 🌐 Etiquette was different around the family table [...] fundamental manners such as asking for food to be passed rather than exercising the ‘boarding-house reach’.
2003		Pasadena Weekly 26 June 🌐 Tables at Old Pasadena’s Buca di Beppo sometimes look as wild as an extended family gathering. A boarding-house reach is needed to nail down a share of the platters.

2. in fig. use, a grab, an easy reach.

1908		L.A. Times 7 Jan. 114: So-called reformers who have a ‘boarding-house reach’ for all the municipal pie in sight, object to the term ‘half-baked.’.
1935		Christian Science Monitor 22 Nov. 15: The Cowboys may have as hard a time as the Tigers did in stopping bounding Bob Hudgens, Bear halfback, when scores are within boarding-house reach.