A training sled, weight sled, or fitness sled is a piece of exercise equipment that provides resistance as the user pushes, pulls, or otherwise moves the sled along a flat surface.[1] Commercial sleds allow easily adjusting the weight or resistance and are supported on feet or wheels that allow moving the sled across surfaces such as grass, turf, or pavement without damage. Training with sleds has become increasingly popular since 2015, due in part to their availability in Crossfit gyms.[2][3] Sled pulling and sled pushing are commonly used forms of training for sprinting.[4]
You [just need] something heavy that you can push along a flat surface.
Cahill was invoked but never defined (see the help page).