They need a certain amount of weight in order to keep a tight grip on the rails.
From the economist.com
If we fight to nationalise the rails we fight for cheaper fares and decent work.
From the guardian.co.uk
He rails at Sein Beda for tuning a recalcitrant drum in the middle of a concert.
From the theatlantic.com
That includes trains, buses, rail bridges, rails, stations and other facilities.
From the suntimes.com
The metal rails on the sides were scratching furniture though, so we fixed that.
From the dailyherald.com
Tony Pike is less than happy his unbeaten star Sacred Falls has drawn the rails.
From the nzherald.co.nz
There are dado and picture rails, coving and ceiling roses throughout the house.
From the thisisbristol.co.uk
The automatic window washing machines run on rails on the sides of the building.
From the en.wikipedia.org
Rails developers preferred, but raw talent and drive most important to our team.
From the techcrunch.com
More examples
Railing: a barrier consisting of a horizontal bar and supports
Complain bitterly
Enclose with rails; "rail in the old graves"
Short for railway; "he traveled by rail"; "he was concerned with rail safety"
Track: a bar or pair of parallel bars of rolled steel making the railway along which railroad cars or other vehicles can roll
A horizontal bar (usually of wood or metal)
An approach lighting system, or ALS, is a lighting system installed on the approach end of an airport runway and consisting of a series of lightbars, strobe lights, or a combination of the two that extends outward from the runway end. ...
Rail is a short 13.5 minute documentary film made by Geoffrey Jones for British Transport Films between 1963 and 1967, prompted by the success of Snow. ...
Rail was an Australian band from Melbourne in the late 1990s. Dan Vertessy was the lead singer and songwriter. They featured Ashley Naylor from Even on guitar and released two albums of guitar pop. Their first album was titled Bad Hair Life, and contained the single "Immune Deficiency". ...