Land Holdings: Acres, Roods, & Perches
Land is typically measured by Rods & Chains.
In a field each villager would have a certain number of strips typically 1 rod wide and the length of the field, generally 1 furlong or less, thus the length of a rod needed to be standardized for a particular place. The standard has come to be 16.5 ft in the US and where feet are mentioned in this post that is the standard used.
Note 1 chain = 4 rods
and 10 chains is a furlong (long furrow, or furrow length)
So, an acre is 1 chain (66 ft) x 10 chains (660 ft).
Freeholds & copyholds tend to define the fields one owns in acres.
A rood is 1/4 acre so could be 1 rod x 5 chains or 1 chain by 2 & 1/2 chains (2 chains + 2 rods).
Houses & gardens (toft & croft) would tend to be in roods, be it 1/4 rood, 1/2 rood, 1 rood, or even 2 roods. Thus the typical rood would likely be 2 rods x 20 rods (5 chains) or 4 rods x 10 rods or some portion thereof around the building, with any remainder in a communal garden area.
Communal garden areas would likely 1 rod by 10 chains per rood (or portion thereof).
A perch is 1/40th of a rood. If you have been paying attention then you know this is 1 rod by 1 rod (aka 16.5 ft square), and would be used to measure out limits if a cottager had only a small portion of a rood in communal gardens. They could well have a cottage on say a small 33ft by 132ft lot (2 rods x 8 rods so 16 perches) and then even if only holding 1/2 rood still have 4 perches in communal garden area (or such).
Now for the fun bit .. all the exact measurements in feet could be hogwash if the standard (local) rod is not exactly 16.5 feet, but the number of rods & chains could be the same even if a local rod was say 12 feet or 20 feet. The length of a standard local rod was typically chiseled into a stone edifice such as the local church so that a permanent guideline was maintained throughout the ages as a long stick (rod) could otherwise be cut to any length.
Hope that helps people understand Rods & Perches, Chains, Roods, & Acres