non rising stem gate valve:

Non-rising stem gate valve is used where vertical space is limited or underground. The stem is threaded into the gate. As the handwheel on the stem is rotated, the gate travels up or down the stem on the threads while the stem remains vertically stationary. This type of valve has a pointer indicator threaded onto the upper end of the stem to indicate the position of the gate.

Features:
Bolted bonnet
Outside screw and yoke
rising stem and non-rising handwheel
Flexible wedge, fully guided
Metal-to-metal seat
renewable seat ring and stem backseat
manual operation standard, gear operator and actuation available
butt weld end
flange end: raised face or ring type joint