Rail is 100% height by default

src/definitions/elements/rail.less

@@ -25,10 +25,10 @@
 *******************************/
 
 .ui.rail {
-  font-size: @size;
   position: absolute;
   top: 0%;
   width: @width;
+  height: @height;
   box-sizing: @contentSizing;
 }
 
@@ -120,7 +120,7 @@
 ---------------*/
 
 .ui.rail {
-  font-size: @size;
+  font-size: @medium;
 }
 
 

src/themes/default/elements/rail.variables

@@ -8,7 +8,7 @@
 
 @contentSizing: content-box;
 @width: 300px;
-@size: 1em;
+@height: 100%;
 @distance: 4rem;
 
 /*-------------------
@@ -22,3 +22,5 @@
 /* Divided */
 @dividedBorder: 1px solid @borderColor;
 @dividedDistance: 5rem;
+
+@medium: 1em;