They are easily applied with a screw and Phillips screwdriver. The screws are supplied with this item. Each spike has a tap on the bottom in which the screw is applied. 

Description and Specs:
height: approx. 1 1/4 inch, 30 mm
base diameter: 3/8 inch, 9.5 mm
material: nickel plaque
finish: Silver nickel
color: Silver
screw type: inch #8-32 x 3/8" length thread
shape: standard tree
Bag size: 20 spikes