Here is the carriage for a three-eights scale naval gun. Note that the cap squares are attached with chin bolts (rear), and are held shut with tapered “keys” to facilitate removal of the barrel for transport and cleaning. The wedge-shaped “quoin” at the back of the carriage is for adjusting the elevation of the barrel. It has a tongue that rides in a dove-tailed groove. All the bolts run through the carriage.