Learn Danish: Silken har en blød overflade, men brættet er ru. - The silk has a soft surface, but the board is rough.

This relates to your current lesson! While most adjectives add a -t to match a neuter (et) word, adjectives ending in the vowel -u (like ru meaning rough, or snu meaning sly) are an exception. They do not add a -t and stay exactly the same in both the en-form and et-form.

Why does brættet have a double consonant in the middle?

The dictionary form is et bræt (a board). Because it is a short word ending in a single consonant right after a short vowel, we double the final consonant when adding the definite suffix -et (the). This spelling rule shows that the vowel sound stays short.

Why does blød not take an ending like -t or -e here?

It describes en overflade (a surface), which is a singular en-word. Adjectives keep their base dictionary form without any endings when they directly describe a singular common-gender noun.

How can I easily remember the gender of a compound word like overflade?

Compound words always take the gender of their final part. Since flade (flat area/surface) is an en-word, the whole word overflade is also an en-word. You can also easily spot this because it uses the article en right before the adjective.