43kg fishplates of four holes 

Fishplates are usually 600mm long, used in pairs either side of the rail ends and bolted together
(usually six, but sometimes four bolts per joint). The bolts may be oppositely-oriented so that
in the event of a derailment and a wheel flange striking the joint, only some of the bolts will be
sheared, reducing the likelihood of the rails misailiging with each other and exacerbating the
seriousness of the derailment. 

http://www.jhint.cc/products/steel-rail/support-steel/134.html