| Solution | Length | |
|---|---|---|
| 3 letters | ||
| oak | 3 | |
| elm | 3 | |
| 4 letters | ||
| pine | 4 | |
| wiry | 4 | |
| ropy | 4 | |
| teak | 4 | |
| 5 letters | ||
| ebony | 5 | |
| larch | 5 | |
| oaken | 5 | |
| tough | 5 | |
| vital | 5 | |
| sound | 5 | |
| stout | 5 | |
| stiff | 5 | |
| solid | 5 | |
| rigid | 5 | |
| hardy | 5 | |
| 6 letters | ||
| sinewy | 6 | |
| torpid | 6 | |
| sturdy | 6 | |
| VISCID | 6 | |
| static | 6 | |
| steady | 6 | |
| strong | 6 | |
| rugged | 6 | |
| stable | 6 | |
| 7 letters | ||
| stringy | 7 | |
| abiding | 7 | |
| cypress | 7 | |
| lasting | 7 | |
| 8 letters | ||
| constant | 8 | |
| stubborn | 8 | |
| unfading | 8 | |
| UNTIRING | 8 | |
| vigorous | 8 | |
| 9 letters | ||
| unchecked | 9 | |
| tenacious | 9 | |
| quiescent | 9 | |
| resistant | 9 | |
| UNFAILING | 9 | |
| sustained | 9 | |
| UNVARYING | 9 | |
| steadfast | 9 | |
| permanent | 9 | |
| well-made | 9 | |
| unaltered | 9 | |
| REMAINING | 9 | |
| 10 letters | ||
| stationary | 10 | |
| persistent | 10 | |
| CONTINUING | 10 | |
| madetolast | 10 | |
| well-built | 10 | |
| UNCHANGING | 10 | |
| UNYIELDING | 10 | |
| 11 letters | ||
| BUILTTOLAST | 11 | |
| hardwearing | 11 | |
| undestroyed | 11 | |
| serviceable | 11 | |
| SUBSTANTIAL | 11 | |
| longlasting | 11 | |
| 12 letters | ||
| UNCHANGEABLE | 12 | |
| 13 letters | ||
| well-grounded | 13 | |